The general rule is that any gift is a taxable gift (IRS Publication 559 Survivors, Executors, and Administrators, on page 25). See below for exceptions.
TaxAct supports the individual tax return but does not support Form 709 United States Gift (and Generation-Skipping Transfer) Tax Return. This is a separate return from the individual tax return (Form 1040 U.S. Individual Income Tax Return).
The gift exclusion for 2020 is $15,000.
See IRS Publication 559 for more information regarding the gift tax.
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.