# Pre-fund Balance

[API Reference](https://docs.credyt.ai/api/customer-wallet-ops-create-adjustment.md)

To make testing easier, you can pre-fund your customer's balance without going through the full payment flow. This is the fastest way to see real-time billing in action!

You can use the [Wallet Adjustment API](https://docs.credyt.ai/api/customer-wallet-ops-create-adjustment.md) to pre-fund a customer’s wallet. For the full overview of how top-ups work in production, check out the [Top-ups and Wallets guide](https://docs.credyt.ai/features/wallets-and-topups.md).

You can use this API for any kind of balance adjustment including external PSP payments, refunds, and promotional credits. A detailed explanation of this functionality is available in our [Adjustments guide](https://docs.credyt.ai/advanced-topics/adjustments-charges-gifts.md).

### Example[​](#example "Direct link to Example")

* REST API
* TypeScript SDK
* Python SDK

POST https\://api.credyt.ai/customers/{customerId}/wallet/adjustments

```json
{
  "transaction_id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
  "asset": "USD",
  "amount": 20,
  "reason": "external_topup",
  "metadata": {
    "psp": "stripe",
    "payment_intent": "pi_3RjbbNJNSIruR1rb0GwMGpH0"
  }
}

```

**Response**

```json
{
  "id": "61e15192-a156-4af4-a3cc-ec6c937795fa",
  "created_at": "2025-10-17T21:00:56.743379Z"
}

```

```typescript
await client.customerWalletOps.createAdjustment({
  transactionId: "3fa85f64-5717-4562-b3fc-2c963f66afa6",
  asset: "USD",
  amount: 20,
  reason: "external_topup",
  metadata: {
    psp: "stripe",
    paymentIntent: "pi_3RjbbNJNSIruR1rb0GwMGpH0",
  },
});

```

[View full sample on GitHub](https://github.com/credyt/sdk-ts/blob/main/samples/walletsCustomerWalletOpsCreateAdjustmentSample.ts#L92)

**SDK response object**

```typescript
const response = {
  id: "61e15192-a156-4af4-a3cc-ec6c937795fa",
  createdAt: "2025-10-17T21:00:56.743379Z",
};

```

```python
response = client.customer_wallet_ops.create_adjustment(
    body={
    "transaction_id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
    "asset": "USD",
    "amount": 20,
    "reason": "external_topup",
    "metadata": {
      "psp": "stripe",
      "payment_intent": "pi_3RjbbNJNSIruR1rb0GwMGpH0",
    },
  },
)

```

**SDK response object**

```python
response = {
  "id": "61e15192-a156-4af4-a3cc-ec6c937795fa",
  "created_at": "2025-10-17T21:00:56.743379Z",
}

```

Wallet Idempotency

Wallet adjustments can be safely retried by specifying the same unique transaction identifier (UUID)