# Instrument Specific Fees

In Finix, `Payment Instruments` are tied to the owner of that account. For example, `Payment Instruments` tied to buyer will be the cards used for purchases while `Payment Instruments` tied to a `Merchant` are the bank accounts where they receive settlements.

Therefore when billing events occur that are tied to a buyer's `Payment Instrument` (e.g. enrolling in account updater, using Plaid for tokenization, etc) Finix cannot automatically map those fees to a specific `Merchant`. By default, these costs are instead charged to your `Application` (e.g. the Platform, Marketplace, Vertical Saas owner's account) and will be deducted from your residual. If you wish to monetize these offerings or pass the fees on to your `Merchant` you must explicitly link the buyers `Payment Instrument` to a `Merchant` resource using the `Payment Instrument Association` [resource](/api/payment-instrument-associations).

To accomplish this example, we will need to:

1. Make sure the Merchant `Fee Profile` is configured with a fee (i.e. has a value >0) for these relevant instrument fees
2. Create a `Payment Instrument Association` resource after the `Payment Instrument` is tokenized.



```
curl -i -X POST \
  -u USfdccsr1Z5iVbXDyYt7hjZZ:313636f3-fac2-45a7-bff7-a334b93e7bda \
  https://finix.sandbox-payments-api.com/payment_instrument_associations \
  -H 'Content-Type: application/json' \
  -H 'Finix-Version: 2022-02-01' \
  -d '{
      "merchant_id": "MUcgYZswyRfqSSbvMsxuaHxZ",
      "payment_instrument_id": "PInQ4yKVvyJxB6dJtQkXLMWt"
  }'
```