# Fix 403 INSUFFICIENT_BALANCE and billing_error

> Why BigModel.io returns 403 INSUFFICIENT_BALANCE or billing_error, 402 for video and spend caps, how prepaid USD balance works, and how to keep calling free models.

Web version: https://bigmodel.io/docs/error-insufficient-balance · Updated 2026-10-27

Requests stop with this error once your balance cannot pay for them:

```json
{ "code": "INSUFFICIENT_BALANCE", "message": "Insufficient balance. Top up at https://bigmodel.io/purchase to continue.", "error": { "message": "Insufficient balance. Top up at https://bigmodel.io/purchase to continue.", "type": "permission_error", "code": "INSUFFICIENT_BALANCE" } }
```

## What it means

BigModel.io is prepaid: each request is charged from your US-dollar balance at the model's listed price. When the balance is zero or below, paid models return **403**. Image, video and audio tasks return **402 `insufficient_balance`** when the balance cannot cover the estimated cost plus your unfinished tasks. Failed requests are never charged.

A **402 `spend_cap_reached`** is different: you reached a weekly or monthly spending cap you set yourself. It has a `Retry-After` header with the seconds until the cap resets.

## How to fix it

1. [Top up](https://bigmodel.io/purchase) your balance. The balance updates as soon as the payment is confirmed.
2. Check per-key quotas in [API Keys](https://bigmodel.io/keys): a key's own USD quota returns 429 `API_KEY_QUOTA_EXHAUSTED`, not 403.
3. For `spend_cap_reached`, wait for the reset or raise the cap on [Balance & billing](https://bigmodel.io/purchase).
4. With a zero balance you can still call models priced at $0, within a per-minute limit. See [Trial credit and free models](https://bigmodel.io/docs/free-credits).

## Troubleshooting

**The console shows a balance but requests return 403.** The request's estimated cost, which counts `max_tokens` and your requests still running, is more than what is left. Lower `max_tokens`, wait for running requests to finish, or top up.

**A plan key returns 403 `permission_error` on a media model.** Plan keys cannot use image, video or audio models. Use a pay-as-you-go key.

## Related

- [Billing & top-ups](https://bigmodel.io/docs/billing)
- [Limits & rate limits](https://bigmodel.io/docs/rate-limits)
- [Error codes and responses](https://bigmodel.io/docs/errors)