> ## Documentation Index
> Fetch the complete documentation index at: https://docs.karta.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# Billing & credits

> Prepaid credits, how usage draws them down, and Karta's guarantee that you can never owe more than you've paid.

Karta billing is **prepaid**. Model usage draws down a credit balance you top
up in advance, so there are no metered invoices and no bill shock: an org can
never owe Karta more than it has already paid. When the balance runs out,
requests pause with **402 Payment Required** until you top up.

## Plans

<Note>
  Current plan names, prices, and included credits are shown in the console when
  you choose a plan. They are left off this page so it cannot drift out of sync
  with live pricing.
</Note>

Karta has a free tier to start with no card and no key, paid plans for ongoing
use, and a custom Enterprise plan. Managed plans run on Karta's platform model
key and prepaid credits; bringing your own provider key (BYOK) is a paid-plan
capability - see [BYOK](/platform/byok).

| Plan path         | Token billing            | Karta billing                                     | Use when                                                        |
| ----------------- | ------------------------ | ------------------------------------------------- | --------------------------------------------------------------- |
| Free tier         | Karta platform model key | Included starter credits only.                    | Trying the platform and first agent deploys.                    |
| Managed paid plan | Karta platform model key | Subscription fee plus prepaid credits.            | You want Karta to manage model access.                          |
| BYOK paid plan    | Your provider key        | Subscription fee plus Karta platform-fee credits. | You need provider contracts, rate limits, or account ownership. |
| Enterprise        | Contract-specific        | Contract-specific.                                | You need procurement, security review, or custom terms.         |

## Credits

Credits are face dollars. Buy them in packs from the billing page; pack prices
include payment processing, so receipts show one number. Usage draws the balance
down at the model's token cost plus Karta's platform fee - the current pack
sizes, fee, and any included monthly credit are shown in the console.

* **Auto-refill (optional)** - buy a chosen pack automatically when the
  balance drops below a threshold you set. A **monthly cap is required** when
  enabling it: it bounds the worst case for a runaway agent at your cap plus
  one pack. Failures never block buying manually.
* **Out of credits** - requests return `402` with reason
  `credits_exhausted`. Agents resume the moment the balance is positive
  again.

| Credit state                 | API behavior                                          | Operator action                                                                     |
| ---------------------------- | ----------------------------------------------------- | ----------------------------------------------------------------------------------- |
| Positive balance             | Requests can run, subject to budgets and rate limits. | Watch usage against budget.                                                         |
| Low balance                  | Requests still run.                                   | Top up manually or enable auto-refill.                                              |
| Exhausted balance            | New requests return `402` with `credits_exhausted`.   | Buy credits; retry once the balance is positive.                                    |
| Payment confirmation pending | Credit may not appear immediately after checkout.     | Wait for the payment confirmation; avoid repeated purchases unless you intend them. |

## Rate card

Model usage is priced per token, tracking the model vendors' published API
pricing; the current per-model rates are shown in the console. On managed plans,
the credit drawdown is the token cost plus Karta's platform fee. On BYOK, you
pay your provider directly for tokens and Karta charges only the platform fee.

## The prepaid guarantee

* No code path can bill you past your collected balance. Usage can briefly
  overshoot by the in-flight turn (agents finish their current response);
  the overshoot is absorbed by Karta, never invoiced.
* Refunds and chargebacks are deducted from the credit balance; if it goes
  negative, usage pauses until a top-up - never a bill.
* The plan subscription fee is the only recurring charge, and it is flat.

## Recovery checklist

| Symptom                                   | Check                                                           | Fix                                                                                     |
| ----------------------------------------- | --------------------------------------------------------------- | --------------------------------------------------------------------------------------- |
| `402` with `credits_exhausted`            | Billing page credit balance.                                    | Buy a credit pack or enable auto-refill.                                                |
| `402` with another budget reason          | Limits page and [Usage & budgets](/platform/usage-and-budgets). | Raise or remove the relevant hard cap.                                                  |
| BYOK agent paused despite provider credit | Karta credit balance.                                           | Top up Karta credits; provider billing covers model tokens, not the Karta platform fee. |