S Corp K-1 has not yet been received.

[gibsonma]

Our family business, which is operated as an S Corp, closed on 9/30/2020.  It and any other part of the business have yet to be dissolved.  I was just informed by our accountant that due to a lack of information in a timely fashion (thanks to my BIL), he is unable to generate our K1's for 2020.  I have no idea what to do.  Do I just overpay, so that I can avoid part of the penalty and get an extension?  Last year, we received approx. $120,000.

[ee-ea]

 Do I just overpay, so that I can avoid part of the penalty and get an extension? 

Yes, that is the safest way to avoid a penalty for late payment.