same thing happened to me
they cashed my check and then 7 months later told me I did not file
I always keep copies
As a small business I have to file a 940 and 941. In early 2021 the IRS was sending me letters saying I had not paid. I had paid and they had cashed the checks. I had to call them numerous times to straighten out their error. Also snail mailed and faxed them the checks.
They spent a lot of IRS time straightening out money that they wanted while they neglected paying out money that they owed other people.