diff --git a/CLAUDE.md b/CLAUDE.md
index 836cde6..c486be2 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -11,6 +11,7 @@ src/
     config.ts                     - Credential storage (~/.config/lucas/)
     api-client.ts                 - HTTP client with Bearer auth
     output.ts                     - JSON output helpers (success/error)
+    body-builder.ts               - Request body builder with --no-flag unset support
   commands/
     auth/
       login.ts                    - Device authorization flow
@@ -29,6 +30,7 @@ src/
     transfers/
       list.ts                     - List all transfers
       create.ts                   - Create transfer (from, to, amount, exchange-rate)
+      update.ts                   - Update transfer by ID
       delete.ts                   - Delete transfer by ID
     subscriptions/
       list.ts                     - List all subscriptions
@@ -39,6 +41,7 @@ src/
     loans/
       list.ts                     - List all loans
       create.ts                   - Create loan (name, principal, account)
+      update.ts                   - Update loan by ID
       pay.ts                      - Make a loan payment
       delete.ts                   - Delete loan by ID
     stats/
@@ -143,6 +146,7 @@ Login flow writes human-readable output to stderr (not JSON) since it is interac
 | DELETE | /api/transactions/:id            | transactions delete     |
 | GET    | /api/transfers                   | transfers list          |
 | POST   | /api/transfers                   | transfers create        |
+| PUT    | /api/transfers/:id               | transfers update        |
 | DELETE | /api/transfers/:id               | transfers delete        |
 | GET    | /api/subscriptions               | subscriptions list      |
 | POST   | /api/subscriptions               | subscriptions create    |
@@ -152,6 +156,7 @@ Login flow writes human-readable output to stderr (not JSON) since it is interac
 | GET    | /api/loans                       | loans list              |
 | POST   | /api/loans                       | loans create            |
 | POST   | /api/loans/:id/pay               | loans pay               |
+| PUT    | /api/loans/:id                   | loans update            |
 | DELETE | /api/loans/:id                   | loans delete            |
 | GET    | /api/stats/summary               | stats summary           |
 | GET    | /api/stats/monthly               | stats monthly           |
diff --git a/README.md b/README.md
index d2a6c28..c8d7066 100644
--- a/README.md
+++ b/README.md
@@ -70,7 +70,11 @@ lucas accounts create \
   --bank "BCP" \
   --currency PEN \
   --balance 1000                    # Create an account
-lucas accounts update <id> --name "New Name"  # Update account
+lucas accounts update <id> \
+  --name "New Name" \
+  --balance 5000 \
+  --credit-limit 10000 \
+  --is-archived true                # Update account
 lucas accounts delete <id>          # Delete account
 ```
 
@@ -117,6 +121,12 @@ lucas transfers create \
   --description "Monthly savings" \
   --exchange-rate 3.72             # Create a transfer
 
+lucas transfers update <id> \
+  --amount 1500 \
+  --exchange-rate 3.75              # Update a transfer
+lucas transfers update <id> \
+  --amount 1000 \
+  --no-notes                        # Update with unset
 lucas transfers delete <id>         # Delete transfer
 ```
 
@@ -128,12 +138,15 @@ lucas subscriptions create \
   --name "Netflix" \
   --amount 44.90 \
   --account-id <id> \
+  --currency PEN \
   --frequency MONTHLY \
+  --billing-day 1 \
   --next-billing-date 2026-04-01   # Create a subscription
 
 lucas subscriptions update <id> \
   --amount 49.90 \
-  --frequency YEARLY               # Update subscription
+  --frequency YEARLY \
+  --no-account-id                  # Update subscription (unset account)
 
 lucas subscriptions mark-paid <id>  # Mark as paid
 lucas subscriptions delete <id>     # Delete subscription
@@ -149,10 +162,21 @@ lucas loans create \
   --name "Car Loan" \
   --principal 25000 \
   --account-id <id> \
+  --currency PEN \
   --interest-rate 12.5 \
   --installments 36 \
+  --first-due-date 2026-02-15 \
+  --interval-unit MONTH \
+  --interval-count 1 \
   --start-date 2026-01-15          # Create a loan
 
+lucas loans update <id> \
+  --name "Auto Loan" \
+  --interest-rate 5.5              # Update a loan
+lucas loans update <id> \
+  --no-agreed-installments \
+  --no-target-payment              # Update with unset
+
 lucas loans pay <id> --amount 750   # Make a payment
 lucas loans delete <id>             # Delete loan
 ```
@@ -180,6 +204,18 @@ lucas exchange-rate convert \
   --amount 100                      # Convert currencies
 ```
 
+### Unsetting Optional Fields
+
+Use `--no-<field>` to clear an optional field:
+
+```bash
+lucas subscriptions update <id> --no-account-id    # Remove linked account
+lucas transactions update <id> --no-category-id    # Clear category
+lucas accounts update <id> --no-credit-limit       # Remove credit limit
+lucas transfers update <id> --no-notes             # Clear notes
+lucas loans update <id> --no-agreed-installments   # Remove agreed installments
+```
+
 ## AI Integration
 
 LucasApp CLI outputs structured JSON exclusively, making it a natural fit for AI agents with terminal access.
diff --git a/package.json b/package.json
index f0b67f1..6b17ed4 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "lucasapp-cli",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "description": "LucasApp CLI - Financial data management for AI agents",
   "author": "StevenACZ",
   "license": "MIT",
diff --git a/src/commands/accounts/update.ts b/src/commands/accounts/update.ts
index bcf1837..ea6ab70 100644
--- a/src/commands/accounts/update.ts
+++ b/src/commands/accounts/update.ts
@@ -1,6 +1,7 @@
 import { Command } from "commander";
 import { apiRequest } from "../../lib/api-client.js";
 import { output } from "../../lib/output.js";
+import { buildBody } from "../../lib/body-builder.js";
 
 export const updateAccountCommand = new Command("update")
   .description("Update an account")
@@ -9,13 +10,33 @@ export const updateAccountCommand = new Command("update")
   .option("--bank <bank>", "Bank name")
   .option("--color <color>", "Account color")
   .option("--icon <icon>", "Account icon")
+  .option("--balance <amount>", "Account balance")
+  .option("--credit-limit <amount>", "Credit limit")
+  .option("--current-debt <amount>", "Current debt")
+  .option("--statement-closing-day <day>", "Statement closing day")
+  .option("--display-order <n>", "Display order")
+  .option("--excluded", "Exclude from totals")
+  .option("--no-excluded", "Include in totals")
+  .option("--is-archived", "Archive account")
+  .option("--no-is-archived", "Unarchive account")
   .action(async (id: string, opts) => {
-    const body: Record<string, unknown> = {};
-    if (opts.name) body.name = opts.name;
-    if (opts.bank) body.bank = opts.bank;
-    if (opts.color) body.color = opts.color;
-    if (opts.icon) body.icon = opts.icon;
-
+    const body = buildBody(opts, [
+      { opt: "name", body: "name" },
+      { opt: "bank", body: "bank" },
+      { opt: "color", body: "color" },
+      { opt: "icon", body: "icon" },
+      { opt: "balance", body: "balance", type: "number" },
+      { opt: "creditLimit", body: "creditLimit", type: "number" },
+      { opt: "currentDebt", body: "currentDebt", type: "number" },
+      {
+        opt: "statementClosingDay",
+        body: "statementClosingDay",
+        type: "number",
+      },
+      { opt: "displayOrder", body: "displayOrder", type: "number" },
+      { opt: "excluded", body: "excluded", type: "boolean" },
+      { opt: "isArchived", body: "isArchived", type: "boolean" },
+    ]);
     const data = await apiRequest("PUT", `/api/accounts/${id}`, body);
     output.success(data);
   });
diff --git a/src/commands/loans/create.ts b/src/commands/loans/create.ts
index 3d9e50a..2935858 100644
--- a/src/commands/loans/create.ts
+++ b/src/commands/loans/create.ts
@@ -1,25 +1,46 @@
 import { Command } from "commander";
 import { apiRequest } from "../../lib/api-client.js";
 import { output } from "../../lib/output.js";
+import { buildBody } from "../../lib/body-builder.js";
 
 export const createLoanCommand = new Command("create")
   .description("Create a new loan")
   .requiredOption("--name <name>", "Loan name")
   .requiredOption("--principal <amount>", "Principal amount")
-  .requiredOption("--account-id <id>", "Account ID")
+  .requiredOption("--currency <code>", "Currency code")
+  .requiredOption("--first-due-date <date>", "First due date (YYYY-MM-DD)")
+  .requiredOption(
+    "--interval-unit <unit>",
+    "Interval unit (DAY|WEEK|MONTH|YEAR)",
+  )
+  .requiredOption("--interval-count <n>", "Interval count")
+  .option("--account-id <id>", "Payment account ID")
+  .option("--agreed-installments <n>", "Total installments")
+  .option("--target-payment <amount>", "Target payment amount")
   .option("--interest-rate <rate>", "Interest rate")
-  .option("--installments <n>", "Number of installments")
-  .option("--start-date <date>", "Start date (YYYY-MM-DD)")
+  .option("--interest-rate-unit <unit>", "Rate unit (ANNUAL|MONTHLY)")
+  .option("--interest-enabled", "Enable interest")
+  .option("--late-fee-amount <amount>", "Late fee amount")
+  .option("--late-fee-grace-days <n>", "Late fee grace days")
+  .option("--late-fee-enabled", "Enable late fees")
   .action(async (opts) => {
-    const body: Record<string, unknown> = {
-      name: opts.name,
-      principal: Number(opts.principal),
-      accountId: opts.accountId,
-    };
-    if (opts.interestRate) body.interestRate = Number(opts.interestRate);
-    if (opts.installments) body.installments = Number(opts.installments);
-    if (opts.startDate) body.startDate = opts.startDate;
-
+    const body = buildBody(opts, [
+      { opt: "name", body: "name" },
+      { opt: "principal", body: "principal", type: "number" },
+      { opt: "currency", body: "currency" },
+      { opt: "firstDueDate", body: "firstDueDate" },
+      { opt: "intervalUnit", body: "intervalUnit" },
+      { opt: "intervalCount", body: "intervalCount", type: "number" },
+      { opt: "accountId", body: "paymentAccountId" },
+      { opt: "agreedInstallments", body: "agreedInstallments", type: "number" },
+      { opt: "targetPayment", body: "targetPayment", type: "number" },
+      { opt: "interestRate", body: "interestRate", type: "number" },
+      { opt: "interestRateUnit", body: "interestRateUnit" },
+      { opt: "interestEnabled", body: "interestEnabled", type: "boolean" },
+      { opt: "lateFeeAmount", body: "lateFeeAmount", type: "number" },
+      { opt: "lateFeeGraceDays", body: "lateFeeGraceDays", type: "number" },
+      { opt: "lateFeeEnabled", body: "lateFeeEnabled", type: "boolean" },
+    ]);
     const data = await apiRequest("POST", "/api/loans", body);
     output.success(data);
   });
diff --git a/src/commands/loans/update.ts b/src/commands/loans/update.ts
new file mode 100644
index 0000000..a440338
--- /dev/null
+++ b/src/commands/loans/update.ts
@@ -0,0 +1,48 @@
+import { Command } from "commander";
+import { apiRequest } from "../../lib/api-client.js";
+import { output } from "../../lib/output.js";
+import { buildBody } from "../../lib/body-builder.js";
+
+export const updateLoanCommand = new Command("update")
+  .description("Update a loan")
+  .argument("<id>", "Loan ID")
+  .option("--name <name>", "Loan name")
+  .option("--account-id <id>", "Payment account ID")
+  .option("--is-primary", "Set as primary")
+  .option("--no-is-primary", "Unset primary")
+  .option("--is-archived", "Archive loan")
+  .option("--no-is-archived", "Unarchive loan")
+  .option("--first-due-date <date>", "First due date (YYYY-MM-DD)")
+  .option("--interval-unit <unit>", "Interval unit (DAY|WEEK|MONTH|YEAR)")
+  .option("--interval-count <n>", "Interval count")
+  .option("--agreed-installments <n>", "Total installments")
+  .option("--target-payment <amount>", "Target payment amount")
+  .option("--interest-rate <rate>", "Interest rate")
+  .option("--interest-rate-unit <unit>", "Rate unit (ANNUAL|MONTHLY)")
+  .option("--interest-enabled", "Enable interest")
+  .option("--no-interest-enabled", "Disable interest")
+  .option("--late-fee-amount <amount>", "Late fee amount")
+  .option("--late-fee-grace-days <n>", "Late fee grace days")
+  .option("--late-fee-enabled", "Enable late fees")
+  .option("--no-late-fee-enabled", "Disable late fees")
+  .action(async (id, opts) => {
+    const body = buildBody(opts, [
+      { opt: "name", body: "name" },
+      { opt: "accountId", body: "paymentAccountId" },
+      { opt: "isPrimary", body: "isPrimary", type: "boolean" },
+      { opt: "isArchived", body: "isArchived", type: "boolean" },
+      { opt: "firstDueDate", body: "firstDueDate" },
+      { opt: "intervalUnit", body: "intervalUnit" },
+      { opt: "intervalCount", body: "intervalCount", type: "number" },
+      { opt: "agreedInstallments", body: "agreedInstallments", type: "number" },
+      { opt: "targetPayment", body: "targetPayment", type: "number" },
+      { opt: "interestRate", body: "interestRate", type: "number" },
+      { opt: "interestRateUnit", body: "interestRateUnit" },
+      { opt: "interestEnabled", body: "interestEnabled", type: "boolean" },
+      { opt: "lateFeeAmount", body: "lateFeeAmount", type: "number" },
+      { opt: "lateFeeGraceDays", body: "lateFeeGraceDays", type: "number" },
+      { opt: "lateFeeEnabled", body: "lateFeeEnabled", type: "boolean" },
+    ]);
+    const data = await apiRequest("PUT", `/api/loans/${id}`, body);
+    output.success(data);
+  });
diff --git a/src/commands/stats/by-category.ts b/src/commands/stats/by-category.ts
index 6b963f4..3cb0a82 100644
--- a/src/commands/stats/by-category.ts
+++ b/src/commands/stats/by-category.ts
@@ -4,7 +4,15 @@ import { output } from "../../lib/output.js";
 
 export const byCategoryCommand = new Command("by-category")
   .description("Get statistics by category")
-  .action(async () => {
-    const data = await apiRequest("GET", "/api/stats/by-category");
+  .option("--currency <code>", "Currency code")
+  .action(async (opts) => {
+    const params: Record<string, string> = {};
+    if (opts.currency) params.currency = opts.currency;
+    const data = await apiRequest(
+      "GET",
+      "/api/stats/by-category",
+      undefined,
+      params,
+    );
     output.success(data);
   });
diff --git a/src/commands/stats/monthly.ts b/src/commands/stats/monthly.ts
index 3111d09..da49758 100644
--- a/src/commands/stats/monthly.ts
+++ b/src/commands/stats/monthly.ts
@@ -4,7 +4,17 @@ import { output } from "../../lib/output.js";
 
 export const monthlyCommand = new Command("monthly")
   .description("Get monthly statistics")
-  .action(async () => {
-    const data = await apiRequest("GET", "/api/stats/monthly");
+  .option("--currency <code>", "Currency code")
+  .option("--months <n>", "Number of months")
+  .action(async (opts) => {
+    const params: Record<string, string> = {};
+    if (opts.currency) params.currency = opts.currency;
+    if (opts.months) params.months = opts.months;
+    const data = await apiRequest(
+      "GET",
+      "/api/stats/monthly",
+      undefined,
+      params,
+    );
     output.success(data);
   });
diff --git a/src/commands/stats/summary.ts b/src/commands/stats/summary.ts
index 92a4a39..c258de5 100644
--- a/src/commands/stats/summary.ts
+++ b/src/commands/stats/summary.ts
@@ -4,7 +4,15 @@ import { output } from "../../lib/output.js";
 
 export const summaryCommand = new Command("summary")
   .description("Get financial summary")
-  .action(async () => {
-    const data = await apiRequest("GET", "/api/stats/summary");
+  .option("--currency <code>", "Currency code")
+  .action(async (opts) => {
+    const params: Record<string, string> = {};
+    if (opts.currency) params.currency = opts.currency;
+    const data = await apiRequest(
+      "GET",
+      "/api/stats/summary",
+      undefined,
+      params,
+    );
     output.success(data);
   });
diff --git a/src/commands/subscriptions/create.ts b/src/commands/subscriptions/create.ts
index 606c687..ecf0a2c 100644
--- a/src/commands/subscriptions/create.ts
+++ b/src/commands/subscriptions/create.ts
@@ -1,25 +1,41 @@
 import { Command } from "commander";
 import { apiRequest } from "../../lib/api-client.js";
 import { output } from "../../lib/output.js";
+import { buildBody } from "../../lib/body-builder.js";
 
 export const createSubscriptionCommand = new Command("create")
   .description("Create a new subscription")
   .requiredOption("--name <name>", "Subscription name")
   .requiredOption("--amount <amount>", "Subscription amount")
-  .requiredOption("--account-id <id>", "Account ID")
-  .requiredOption("--frequency <freq>", "Frequency (MONTHLY|YEARLY|WEEKLY)")
-  .option("--next-billing-date <date>", "Next billing date")
+  .requiredOption("--frequency <freq>", "Frequency (MONTHLY|YEARLY)")
+  .requiredOption("--billing-day <day>", "Billing day of the month")
+  .option("--account-id <id>", "Account ID")
+  .option("--currency <code>", "Currency code")
+  .option("--billing-month <month>", "Billing month (for YEARLY)")
+  .option("--icon <icon>", "Icon")
+  .option("--color <color>", "Color")
+  .option("--category-id <id>", "Category ID")
+  .option("--type <type>", "Type")
+  .option("--auto-record", "Enable auto-record")
+  .option("--start-date <date>", "Start date (YYYY-MM-DD)")
   .option("--description <desc>", "Description")
   .action(async (opts) => {
-    const body: Record<string, unknown> = {
-      name: opts.name,
-      amount: Number(opts.amount),
-      accountId: opts.accountId,
-      frequency: opts.frequency,
-    };
-    if (opts.nextBillingDate) body.nextBillingDate = opts.nextBillingDate;
-    if (opts.description) body.description = opts.description;
-
+    const body = buildBody(opts, [
+      { opt: "name", body: "name" },
+      { opt: "amount", body: "amount", type: "number" },
+      { opt: "frequency", body: "frequency" },
+      { opt: "billingDay", body: "billingDay", type: "number" },
+      { opt: "accountId", body: "accountId" },
+      { opt: "currency", body: "currency" },
+      { opt: "billingMonth", body: "billingMonth", type: "number" },
+      { opt: "icon", body: "icon" },
+      { opt: "color", body: "color" },
+      { opt: "categoryId", body: "categoryId" },
+      { opt: "type", body: "type" },
+      { opt: "autoRecord", body: "autoRecord", type: "boolean" },
+      { opt: "startDate", body: "startDate" },
+      { opt: "description", body: "description" },
+    ]);
     const data = await apiRequest("POST", "/api/subscriptions", body);
     output.success(data);
   });
diff --git a/src/commands/subscriptions/update.ts b/src/commands/subscriptions/update.ts
index 840fc4b..d71090a 100644
--- a/src/commands/subscriptions/update.ts
+++ b/src/commands/subscriptions/update.ts
@@ -1,23 +1,46 @@
 import { Command } from "commander";
 import { apiRequest } from "../../lib/api-client.js";
 import { output } from "../../lib/output.js";
+import { buildBody } from "../../lib/body-builder.js";
 
 export const updateSubscriptionCommand = new Command("update")
   .description("Update a subscription")
   .argument("<id>", "Subscription ID")
   .option("--name <name>", "Subscription name")
   .option("--amount <amount>", "Amount")
-  .option("--frequency <freq>", "Frequency (MONTHLY|YEARLY|WEEKLY)")
-  .option("--next-billing-date <date>", "Next billing date")
+  .option("--frequency <freq>", "Frequency (MONTHLY|YEARLY)")
   .option("--description <desc>", "Description")
+  .option("--currency <code>", "Currency code")
+  .option("--account-id <id>", "Account ID")
+  .option("--billing-day <day>", "Billing day of the month")
+  .option("--billing-month <month>", "Billing month (for YEARLY)")
+  .option("--icon <icon>", "Icon")
+  .option("--color <color>", "Color")
+  .option("--category-id <id>", "Category ID")
+  .option("--type <type>", "Type")
+  .option("--start-date <date>", "Start date (YYYY-MM-DD)")
+  .option("--auto-record", "Enable auto-record")
+  .option("--no-auto-record", "Disable auto-record")
+  .option("--is-active", "Activate subscription")
+  .option("--no-is-active", "Deactivate subscription")
   .action(async (id: string, opts) => {
-    const body: Record<string, unknown> = {};
-    if (opts.name) body.name = opts.name;
-    if (opts.amount) body.amount = Number(opts.amount);
-    if (opts.frequency) body.frequency = opts.frequency;
-    if (opts.nextBillingDate) body.nextBillingDate = opts.nextBillingDate;
-    if (opts.description) body.description = opts.description;
-
+    const body = buildBody(opts, [
+      { opt: "name", body: "name" },
+      { opt: "amount", body: "amount", type: "number" },
+      { opt: "frequency", body: "frequency" },
+      { opt: "description", body: "description" },
+      { opt: "currency", body: "currency" },
+      { opt: "accountId", body: "accountId" },
+      { opt: "billingDay", body: "billingDay", type: "number" },
+      { opt: "billingMonth", body: "billingMonth", type: "number" },
+      { opt: "icon", body: "icon" },
+      { opt: "color", body: "color" },
+      { opt: "categoryId", body: "categoryId" },
+      { opt: "type", body: "type" },
+      { opt: "startDate", body: "startDate" },
+      { opt: "autoRecord", body: "autoRecord", type: "boolean" },
+      { opt: "isActive", body: "isActive", type: "boolean" },
+    ]);
     const data = await apiRequest("PUT", `/api/subscriptions/${id}`, body);
     output.success(data);
   });
diff --git a/src/commands/transactions/update.ts b/src/commands/transactions/update.ts
index 0304d4e..c4196e6 100644
--- a/src/commands/transactions/update.ts
+++ b/src/commands/transactions/update.ts
@@ -1,23 +1,28 @@
 import { Command } from "commander";
 import { apiRequest } from "../../lib/api-client.js";
 import { output } from "../../lib/output.js";
+import { buildBody } from "../../lib/body-builder.js";
 
 export const updateTransactionCommand = new Command("update")
   .description("Update a transaction")
   .argument("<id>", "Transaction ID")
   .option("--description <desc>", "Transaction description")
   .option("--amount <amount>", "Transaction amount")
+  .option("--type <type>", "Type (INCOME|EXPENSE)")
+  .option("--date <date>", "Date (YYYY-MM-DD)")
   .option("--category-id <id>", "Category ID")
   .option("--notes <notes>", "Additional notes")
   .option("--merchant <merchant>", "Merchant name")
   .action(async (id: string, opts) => {
-    const body: Record<string, unknown> = {};
-    if (opts.description) body.description = opts.description;
-    if (opts.amount) body.amount = Number(opts.amount);
-    if (opts.categoryId) body.categoryId = opts.categoryId;
-    if (opts.notes) body.notes = opts.notes;
-    if (opts.merchant) body.merchant = opts.merchant;
-
+    const body = buildBody(opts, [
+      { opt: "description", body: "description" },
+      { opt: "amount", body: "amount", type: "number" },
+      { opt: "type", body: "type" },
+      { opt: "date", body: "date" },
+      { opt: "categoryId", body: "categoryId" },
+      { opt: "notes", body: "notes" },
+      { opt: "merchant", body: "merchant" },
+    ]);
     const data = await apiRequest("PUT", `/api/transactions/${id}`, body);
     output.success(data);
   });
diff --git a/src/commands/transfers/create.ts b/src/commands/transfers/create.ts
index 9466e96..b89a94f 100644
--- a/src/commands/transfers/create.ts
+++ b/src/commands/transfers/create.ts
@@ -1,23 +1,29 @@
 import { Command } from "commander";
 import { apiRequest } from "../../lib/api-client.js";
 import { output } from "../../lib/output.js";
+import { buildBody } from "../../lib/body-builder.js";
 
 export const createTransferCommand = new Command("create")
   .description("Create a new transfer")
   .requiredOption("--from-account-id <id>", "Source account ID")
   .requiredOption("--to-account-id <id>", "Destination account ID")
   .requiredOption("--amount <amount>", "Transfer amount")
+  .option("--to-amount <amount>", "Destination amount (cross-currency)")
   .option("--description <desc>", "Transfer description")
+  .option("--date <date>", "Date (YYYY-MM-DD)")
+  .option("--notes <notes>", "Notes")
   .option("--exchange-rate <rate>", "Exchange rate")
   .action(async (opts) => {
-    const body: Record<string, unknown> = {
-      fromAccountId: opts.fromAccountId,
-      toAccountId: opts.toAccountId,
-      amount: Number(opts.amount),
-    };
-    if (opts.description) body.description = opts.description;
-    if (opts.exchangeRate) body.exchangeRate = Number(opts.exchangeRate);
-
+    const body = buildBody(opts, [
+      { opt: "fromAccountId", body: "fromAccountId" },
+      { opt: "toAccountId", body: "toAccountId" },
+      { opt: "amount", body: "amount", type: "number" },
+      { opt: "toAmount", body: "toAmount", type: "number" },
+      { opt: "description", body: "description" },
+      { opt: "date", body: "date" },
+      { opt: "notes", body: "notes" },
+      { opt: "exchangeRate", body: "exchangeRate", type: "number" },
+    ]);
     const data = await apiRequest("POST", "/api/transfers", body);
     output.success(data);
   });
diff --git a/src/commands/transfers/update.ts b/src/commands/transfers/update.ts
new file mode 100644
index 0000000..1a6bf25
--- /dev/null
+++ b/src/commands/transfers/update.ts
@@ -0,0 +1,26 @@
+import { Command } from "commander";
+import { apiRequest } from "../../lib/api-client.js";
+import { output } from "../../lib/output.js";
+import { buildBody } from "../../lib/body-builder.js";
+
+export const updateTransferCommand = new Command("update")
+  .description("Update a transfer")
+  .argument("<id>", "Transfer ID")
+  .requiredOption("--amount <amount>", "Transfer amount")
+  .option("--to-amount <amount>", "Destination amount (cross-currency)")
+  .option("--description <desc>", "Description")
+  .option("--date <date>", "Date (YYYY-MM-DD)")
+  .option("--notes <notes>", "Notes")
+  .option("--exchange-rate <rate>", "Exchange rate")
+  .action(async (id, opts) => {
+    const body = buildBody(opts, [
+      { opt: "amount", body: "amount", type: "number" },
+      { opt: "toAmount", body: "toAmount", type: "number" },
+      { opt: "description", body: "description" },
+      { opt: "date", body: "date" },
+      { opt: "notes", body: "notes" },
+      { opt: "exchangeRate", body: "exchangeRate", type: "number" },
+    ]);
+    const data = await apiRequest("PUT", `/api/transfers/${id}`, body);
+    output.success(data);
+  });
diff --git a/src/index.ts b/src/index.ts
index e18abfd..e8d21e5 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -21,6 +21,7 @@ import { deleteTransactionCommand } from "./commands/transactions/delete.js";
 // Transfers
 import { listTransfersCommand } from "./commands/transfers/list.js";
 import { createTransferCommand } from "./commands/transfers/create.js";
+import { updateTransferCommand } from "./commands/transfers/update.js";
 import { deleteTransferCommand } from "./commands/transfers/delete.js";
 
 // Subscriptions
@@ -33,6 +34,7 @@ import { markPaidCommand } from "./commands/subscriptions/mark-paid.js";
 // Loans
 import { listLoansCommand } from "./commands/loans/list.js";
 import { createLoanCommand } from "./commands/loans/create.js";
+import { updateLoanCommand } from "./commands/loans/update.js";
 import { payLoanCommand } from "./commands/loans/pay.js";
 import { deleteLoanCommand } from "./commands/loans/delete.js";
 
@@ -82,6 +84,7 @@ transactions.addCommand(deleteTransactionCommand);
 const transfers = program.command("transfers").description("Manage transfers");
 transfers.addCommand(listTransfersCommand);
 transfers.addCommand(createTransferCommand);
+transfers.addCommand(updateTransferCommand);
 transfers.addCommand(deleteTransferCommand);
 
 // Grupo: subscriptions
@@ -98,6 +101,7 @@ subscriptions.addCommand(markPaidCommand);
 const loans = program.command("loans").description("Manage loans");
 loans.addCommand(listLoansCommand);
 loans.addCommand(createLoanCommand);
+loans.addCommand(updateLoanCommand);
 loans.addCommand(payLoanCommand);
 loans.addCommand(deleteLoanCommand);
 
diff --git a/src/lib/body-builder.ts b/src/lib/body-builder.ts
new file mode 100644
index 0000000..d94f72b
--- /dev/null
+++ b/src/lib/body-builder.ts
@@ -0,0 +1,25 @@
+type FieldType = "number" | "boolean" | "string";
+
+interface FieldMapping {
+  opt: string;
+  body: string;
+  type?: FieldType;
+}
+
+export function buildBody(
+  opts: Record<string, unknown>,
+  fields: FieldMapping[],
+): Record<string, unknown> {
+  const body: Record<string, unknown> = {};
+  for (const { opt, body: key, type } of fields) {
+    const val = opts[opt];
+    if (val === false) {
+      body[key] = null;
+    } else if (val !== undefined) {
+      if (type === "number") body[key] = Number(val);
+      else if (type === "boolean") body[key] = true;
+      else body[key] = val;
+    }
+  }
+  return body;
+}