# How To Pay Transaction Fee

This tutorial will teach you how to register tokens issued in a multi-chain environment as system tokens and use them as gas fees.

### Tutorial Objectives

By completing this tutorial, you will be able to:

* Build a `RelayChain <> Parachain` test network using a zombie network.
* Propose governance to register tokens issued in a parachain as system tokens in the relay chain.
* After governance approval, pay gas fees with the system tokens issued in the parachain.

### Before You Start

Before you start, make sure to:

* [Simulate a Parachain Network Using a Zombie Network](https://github.com/InfraBlockchainTeam/infrablockspace-docs/blob/master/en/infrablockchain/tutorials/basic/test/simulate-parachains.md)
* Complete the preparation to pay transaction fees with the system token through the [System Token Registration Process](https://docs.infrablockchain.net/infrablockchain-docs/infrablockchain/tutorials/basic/how-to-interact-with-system-token).

### Using System Tokens as Gas Fees

Let's call the `transfer` transaction of Assets as follows:

![parachain\_asset\_transfer](https://3394686052-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F5FcHUSDzEQOuSRhER7FQ%2Fuploads%2Fgit-blob-1d27cb895b0eeb70fb695e2202116b91f0e61319%2Fparachain_asset_transfer.png?alt=media)

Specify the token to be used as the transaction fee.

![send\_transaction](https://3394686052-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F5FcHUSDzEQOuSRhER7FQ%2Fuploads%2Fgit-blob-d5d9427032cc5315bdf39ffaf691aa52af525c37%2Fsend_transaction.png?alt=media)

When the transaction is executed successfully, you can see the event that the transaction fee was paid with the system token as follows:

![tx\_fee\_paid\_event](https://3394686052-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F5FcHUSDzEQOuSRhER7FQ%2Fuploads%2Fgit-blob-2512cdf8d3b2d17169c87e8efdb55f61eb41c974%2Ftx_fee_paid_event.png?alt=media)