how to amend 2020 form 1065 to incorporate corrected form 1099 increasing gross revenue?

[Accountant-Man]

Check the box on page 1. I think it's called "amended."

[sjrcpa]

If you're allowed to amend. You can't if it's a BBA partnership. Then you have to do an Administrative Adjustment Request.

[rbynaker]

The bigger problem is that gross income should not be determined by a 1099 form.  The partnership is required to keep books and records.  Those books and records should properly record income.

This begs the question, what else is not being reported?