diff --git a/routstr/balance.py b/routstr/balance.py
index 03ddf36c..91b19ce5 100644
--- a/routstr/balance.py
+++ b/routstr/balance.py
@@ -109,13 +109,19 @@ async def account_info(
 # Note: validate_bearer_key already supports refund_address and key_expiry_time params
 
 
-@router.get("/create")
-async def create_balance(
+class BalanceCreateRequest(BaseModel):
+    initial_balance_token: str
+    balance_limit: int | None = None
+    balance_limit_reset: str | None = None
+    validity_date: int | None = None
+
+
+async def _create_balance(
     initial_balance_token: str,
-    balance_limit: int | None = None,
-    balance_limit_reset: str | None = None,
-    validity_date: int | None = None,
-    session: AsyncSession = Depends(get_session),
+    balance_limit: int | None,
+    balance_limit_reset: str | None,
+    validity_date: int | None,
+    session: AsyncSession,
 ) -> dict:
     key = await validate_bearer_key(initial_balance_token, session)
 
@@ -135,6 +141,37 @@ async def create_balance(
     }
 
 
+@router.post("/create")
+async def create_balance_from_body(
+    payload: BalanceCreateRequest,
+    session: AsyncSession = Depends(get_session),
+) -> dict:
+    return await _create_balance(
+        payload.initial_balance_token,
+        payload.balance_limit,
+        payload.balance_limit_reset,
+        payload.validity_date,
+        session,
+    )
+
+
+@router.get("/create")
+async def create_balance(
+    initial_balance_token: str,
+    balance_limit: int | None = None,
+    balance_limit_reset: str | None = None,
+    validity_date: int | None = None,
+    session: AsyncSession = Depends(get_session),
+) -> dict:
+    return await _create_balance(
+        initial_balance_token,
+        balance_limit,
+        balance_limit_reset,
+        validity_date,
+        session,
+    )
+
+
 @router.get("/info")
 async def wallet_info(
     key: ApiKey = Depends(get_key_from_header),
diff --git a/tests/unit/test_balance_create_api.py b/tests/unit/test_balance_create_api.py
new file mode 100644
index 00000000..e1f70f5b
--- /dev/null
+++ b/tests/unit/test_balance_create_api.py
@@ -0,0 +1,40 @@
+from types import SimpleNamespace
+from unittest.mock import AsyncMock
+
+import pytest
+from fastapi import FastAPI
+from httpx import ASGITransport, AsyncClient
+
+from routstr import balance as balance_module
+from routstr.core.db import get_session
+
+
+@pytest.mark.asyncio
+async def test_create_balance_accepts_large_cashu_token_in_post_body(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    token = "cashuA" + "x" * 20_000
+    key = SimpleNamespace(hashed_key="hashed", balance=123_000)
+    validate_bearer_key = AsyncMock(return_value=key)
+    session = AsyncMock()
+    monkeypatch.setattr(balance_module, "validate_bearer_key", validate_bearer_key)
+
+    async def override_get_session():  # type: ignore[no-untyped-def]
+        yield session
+
+    app = FastAPI()
+    app.include_router(balance_module.balance_router)
+    app.dependency_overrides[get_session] = override_get_session
+
+    async with AsyncClient(
+        transport=ASGITransport(app=app),  # type: ignore[arg-type]
+        base_url="http://test",
+    ) as client:
+        response = await client.post(
+            "/v1/balance/create",
+            json={"initial_balance_token": token},
+        )
+
+    assert response.status_code == 200
+    assert response.json() == {"api_key": "sk-hashed", "balance": 123_000}
+    validate_bearer_key.assert_awaited_once_with(token, session)
diff --git a/ui/components/landing/cashu-payment-workflow.tsx b/ui/components/landing/cashu-payment-workflow.tsx
index e2244ea0..0835269c 100644
--- a/ui/components/landing/cashu-payment-workflow.tsx
+++ b/ui/components/landing/cashu-payment-workflow.tsx
@@ -91,25 +91,27 @@ export function CashuPaymentWorkflow({
     setIsCreatingKey(true);
 
     try {
-      const params = new URLSearchParams({
+      const requestPayload: {
+        initial_balance_token: string;
+        balance_limit?: number;
+        balance_limit_reset?: string;
+        validity_date?: number;
+      } = {
         initial_balance_token: initialToken.trim(),
-      });
-      if (balanceLimit) params.append('balance_limit', balanceLimit);
+      };
+      if (balanceLimit) requestPayload.balance_limit = Number(balanceLimit);
       if (balanceLimitReset)
-        params.append('balance_limit_reset', balanceLimitReset);
+        requestPayload.balance_limit_reset = balanceLimitReset;
       if (validityDate) {
-        const timestamp = Math.floor(
+        requestPayload.validity_date = Math.floor(
           new Date(validityDate + 'T23:59:59').getTime() / 1000
         );
-        params.append('validity_date', timestamp.toString());
       }
-      const response = await fetch(
-        `${baseUrl}/v1/balance/create?${params.toString()}`,
-        {
-          method: 'GET',
-          headers: { 'Content-Type': 'application/json' },
-        }
-      );
+      const response = await fetch(`${baseUrl}/v1/balance/create`, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify(requestPayload),
+      });
       if (!response.ok) {
         const errorText = await response.text();
         throw new Error(errorText || 'Failed to create API key');
diff --git a/ui/components/providers/RoutstrCreateKeySection.tsx b/ui/components/providers/RoutstrCreateKeySection.tsx
index 2fecf5eb..2741a0a6 100644
--- a/ui/components/providers/RoutstrCreateKeySection.tsx
+++ b/ui/components/providers/RoutstrCreateKeySection.tsx
@@ -161,13 +161,11 @@ export function RoutstrCreateKeySection({
 
     setIsCreatingCashu(true);
     try {
-      const params = new URLSearchParams({
-        initial_balance_token: cashuToken.trim(),
+      const resp = await fetch(`${cleanUrl}/v1/balance/create`, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ initial_balance_token: cashuToken.trim() }),
       });
-      const resp = await fetch(
-        `${cleanUrl}/v1/balance/create?${params.toString()}`,
-        { method: 'GET', headers: { 'Content-Type': 'application/json' } }
-      );
 
       if (!resp.ok) {
         const errorText = await resp.text();