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

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

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?