I had a payment due which was deducted from my checking account. Today I received a substantial refund. I think this is an error what do I do?

[VolvoGirl]

You had a tax due to the IRS?  And just got a deposit from the IRS?  Did you have any unemployment?  There are big changes for that.  You can exclude up to 10,200 of unemployment unless your income is over 150,000. The IRS will recalculate your return for the new unemployment exemption if you filed before the changes.  

See this new IRS May 14, 2021
https://www.irs.gov/newsroom/irs-begins-correcting-tax-returns-for-unemployment-compensation-income-...

Or it could be the new 3rd Stimulus check.  It is 1400 per person.