question 1

The general acceptance of the government’s fiat money derives from its status as legal tender and from the fact that it is required in payment of federal taxes. Those who have no tax liability have reason to acquire fiat money because it is of value to those who do. Thus fiat money can be viewed as a tax credit, which will be used as a medium of exchange as long as the government widely enforces tax collection.

-----does anyone can help me to understand the red sentence?? thx in advance