Yes I experience a similar result with 2020 Late Penalties and Interest Worksheet. This worksheet also populates the due date of the 2020 individual income tax return on line 3b as 7/15/2020. You may check the box on line 3b and change the due date manually.

That change does not change the calculation of 5a Number of months, or fraction thereof, that payment was late.

You must override line 5a and manually enter the correct number of months and the applicable interest rate periods in Part II. Interest will calculate for the periods the tax remained unpaid or late and continue to calculate for quarterly periods after the tax is expected to be paid.

I believe the Late Penalties and Interest Worksheet in Proseries is designed to be used to calculate late penalties and interest for tax returns that are filed late (filed AFTER the original due of that tax return). .