It is possible that the computations could be different, if you used the 2020 directions on the 2021 form.
The computation for Part III, line 10 of the 2021 version is potentially different that Part IV, line 18 of the 2020 version.
If you owe more or less of a penalty than the IRS’ system computes, you’ll receive a notice and a refund (or bill, as the case may be) reflecting the IRS’ computation.