Hello @ccavella,

You can create a deposit to add the line item with a negative processing fee. Let me show you how.

1. Go to the +New button.
2. Under OTHER, select Bank Deposit.
3. On the Select the payments included in this deposit section, select the payment you recently entered.
4. Below the ACCOUNT column, select your Square or Bank Fees account.
5. Enter the amount of the processing fee. Say -3.
6. Click Save and close.

From here, you can go ahead and match the Square payments with the deposit you've created after following the steps above.

Additionally, I've also included this reference for a compilation of articles you can use while working with us: Banking in QuickBooks.

If there's anything else that I can help you with, please let me know in the comments below. I'll be here to lend a hand.