Per diem rates would be entered on Schedule C (Form 1040), Lines 24a and 24b, for travel and meal expenses.
To enter the Per Diem rates for Federal Schedule C into the TaxAct program:
Note. Enter all of your meals expenses. Your deduction is generally limited to 50% of your total costs, but TaxAct will take care of the math for you. If the taxpayer is subject to the Department of Transportation (DOT) hours of service limits, the deduction is limited to 80%
You can find the current rates on the U.S. General Services Administration's Per Diem Rates website. A searchable Excel file can be downloaded from this site to make finding the applicable rates easier.
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.