If you are using ATX, you would enter the 1099K, assign it to other income, and at the top of Schedule 1 there is a box for amounts that are in error on the 1099K or for personal sales with losses. At least I think that is the wording. But in any case, enter the 1099K and then put the $1,300 in that box and it should go away. I have not had to do this yet so please let me know if it works as advertised.
@jklcpa if this does work, you may want to pin the instructions for this year as it is new and I think we are going to see this question come up a lot during the tax season. Your call, just a thought.
Tom
Longview, TX