# Payment Instrument Associations

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`


## Create a Payment Instrument Association

 - [POST /payment_instrument_associations](https://docs.finix.com/api/payment-instrument-associations/createpaymentinstrumentassociation.md): Create a Payment Instrument Association to associate a Payment Instrument with a Merchant for fee assignment purposes.

## List Payment Instrument Associations

 - [GET /payment_instrument_associations](https://docs.finix.com/api/payment-instrument-associations/listpaymentinstrumentassociations.md): Retrieve a list of Payment Instrument Association resources.

## Fetch a Payment Instrument Association

 - [GET /payment_instrument_associations/{payment_instrument_association_id}](https://docs.finix.com/api/payment-instrument-associations/getpaymentinstrumentassociation.md): Retrieve the details of an existing Payment Instrument Association.

## Update a Payment Instrument Association

 - [PUT /payment_instrument_associations/{payment_instrument_association_id}](https://docs.finix.com/api/payment-instrument-associations/updatepaymentinstrumentassociation.md): Update the tags of an existing Payment Instrument Association.