# 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](/infrablockchain-docs/infrablockchain/tutorials/basic/how-to-interact-with-system-token.md).

### Using System Tokens as Gas Fees

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

![parachain\_asset\_transfer](/files/rZ6c7TucNLYlIUOp1Cuh)

Specify the token to be used as the transaction fee.

![send\_transaction](/files/L0u1gGfPJqUOujg6zHxa)

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](/files/O3eGMFBwsciivh48UaHc)


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