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

# Balances and how fees are charged

> What Credits and gas tokens each pay for, the order a transaction fee is charged in, and how transactions from Cobo Portal differ from those made through the API.

## Credits and gas tokens

|                | Credits                                                                             | Gas tokens                                                    |
| -------------- | ----------------------------------------------------------------------------------- | ------------------------------------------------------------- |
| Funded with    | USDT, USDC, or USD                                                                  | The token each chain charges its fees in, deposited per chain |
| Pays for       | Transaction fees on any supported chain, Cobo monthly bills, and add-on plan quotas | **Transaction fees on its own chain only**                    |
| Cannot pay for | —                                                                                   | Cobo bills                                                    |

## The order a fee is charged in

Cobo looks at three sources, in order:

1. **The gas tokens held by the wallet address itself**
2. **The gas tokens in Billing Center**
3. **Credits**

If none of them is enough, the transaction fails.

Whether step 1 is skipped depends on the sponsorship rule you selected. Step 2 requires gas token top-up to be enabled; without it, the fee goes straight to step 3.

### One fee is paid in full by a single source

<Warning>
  **When a source is not enough, the whole fee moves to the next source — the next source does not top up the difference.**

  For example: the address holds 0.003 ETH and the transaction needs 0.005 ETH. Billing Center does not add the missing 0.002. It **pays the full 0.005**, and the 0.003 already in the address is left untouched.

  The same applies further down: if Billing Center's gas tokens fall short, the entire fee is charged to Credits instead — the gas token balance is not partially spent first.
</Warning>

This matters for reconciliation: every fee in your transaction records is **tagged with exactly one payment source** — Paid with Credits, or Paid with gas token.

## Cobo Portal and the API follow different rules

<Warning>
  **The per-chain sponsorship rules and the deduction preference apply only to transactions initiated through the API. Transfers initiated from Cobo Portal do not read those settings.**
</Warning>

### Transfers initiated from Cobo Portal

The behavior is fixed per chain and is not affected by those settings:

| Chain                 | Fixed behavior                                                                               |
| --------------------- | -------------------------------------------------------------------------------------------- |
| EVM-compatible chains | Use the address's gas tokens if they are enough; otherwise Billing Center pays the whole fee |
| TRON, Solana, Tempo   | Billing Center pays directly                                                                 |

In addition, when a Portal transfer is sponsored and gas tokens fall short, **the entire fee is charged to Credits**.

To stop Billing Center from covering a particular Portal transfer, choose that option in the transfer dialog.

### Transactions initiated through the API

How the fee is paid is determined by the `auto_fuel` parameter in the request. **When the parameter is omitted it defaults to `UsePortalPreference`, which follows the per-chain sponsorship rules configured in Settings.** When another value is passed explicitly, the request decides and the page configuration is not read.

<Note>For all accepted values and request examples, see the [Transfer token](https://www.cobo.com/developers/v2/api-references/transactions/transfer-token) endpoint in the Developer Hub.</Note>