Per diem rates would be entered on Schedule C, Lines 24a and 24b for travel and meal expenses. 

To enter the Per Diem rates for Federal Schedule C into the TaxAct program:

1. From within your TaxAct return (Online or Desktop), click Federal. On smaller devices, click the menu icon in the upper left-hand corner, then select Federal.
2. Click Business Income to expand the category and then click Business income or loss from a sole proprietorship
3. Click +Add Federal Schedule C to create a new copy of the schedule or Review review a schedule already created
4. Enter the expenses on the screen titled Business Income - Meals and Entertainment

Generally, taxpayers may deduct 50% of business meal and entertainment expenses. If the taxpayer is subject to the Department of Transportation (DOT) hours of service limits, the percentage is 80%.

You can find the current rates on the U.S. General Services Administration's website Per Diem Rates. A searchable Excel file can be downloaded from this site to make finding the applicable rates easier.