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

# CustomFee

A transfer fee to assess during a CryptoTransfer that transfers units of the token to which the fee is attached. A custom fee may be either fixed or fractional, and must specify a fee collector account to receive the assessed fees. Only positive fees may be assessed.

| Field                      | Type                                                                | Description                           |
| -------------------------- | ------------------------------------------------------------------- | ------------------------------------- |
| one of fee `{`             |                                                                     |                                       |
| `fixed_fee`                | [FixedFee](/reference/protobuf/token/customfees/fixedfee)           | Fixed fee to be charged               |
| `fractional_fee`           | [FractionalFee](/reference/protobuf/token/customfees/fractionalfee) | Fractional fee to be charged          |
| `royalty_fee`              | [RoyaltyFee](/reference/protobuf/token/customfees/royaltyfee)       | Royalty fee to be charged             |
| `}`                        |                                                                     |                                       |
| `fee_collector_account_id` | [AccountID](/reference/protobuf/basic-types/accountid)              | The account to receive the custom fee |