If you did not report the income from that 1099-K on your tax return, then yes you will need to amend that return to include that 1099-K money.
If you did report that income but did not state it was from a 1099-K, that's OK, you do not need to amend because the IRS receives the same information you do (as long as the total income is reported on your return).
I have added directions below on how to both amend that return and how to enter that 1099-K.
AMEND RETURN
https://ttlc.intuit.com/replies/3288565
HOW TO ENTER 1099-K
My profit and loss statement reports EVERYTHING directly from Quickbooks. The square report is correct with cc transactions, but I accidentally reported some cash and check payments twice on square. Will that show up on the 1099-K or is the 1099-K ONLY for merchant/cc transactions?
The 1099-K is only for merchant/cc transactions. It will not list amounts that you manually entered into Square via the dashboard, etc.
Wow, you are amazingly helpful! Then my taxes are correct and I'll just leave as is.
If you did not report the income from that 1099-K on your tax return, then yes you will need to amend that return to include that 1099-K money.
If you did report that income but did not state it was from a 1099-K, that's OK, you do not need to amend because the IRS receives the same information you do (as long as the total income is reported on your return).
I have added directions below on how to both amend that return and how to enter that 1099-K.
AMEND RETURN
https://ttlc.intuit.com/replies/3288565
HOW TO ENTER 1099-K