Hello @roscheimmigrationlaw ,

As of the moment, there isn't an integrated way to display the mode of payment when sending invoices to your clients.

With this, let's consider letting them know you only accept payment with ACH or use the Memo field of your invoices.

In the same manner. I've also included this reference for a compilation of articles you can use while working with us: Sales and CUstomers for QuickBooks Online.

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.