Can I file single if I got divorced last year and have a divorce decree?

[mathteachingmom]

Your filing status is based on your status on December 31, 2020 for this year's taxes. If your divorce was finalized before that date, as you indicate in your question, then your filing status will be single.

The only change for that status would be if you have a qualifying dependent on your tax return that qualifies you for head of household status.