The gold-standard response to this form of fraud, of course, is to simply quit mailing checks, and use electronic payments, in which you give the payee permission to take the funds directly out of your bank account. No paper, no postage, nothing but swift invisible funds transfer. I always found check-writing, mailing, and checkbook tending tedious, so I adapted to electronic payment readily and gratefully.
But even I, though a sworn enemy of check mailing, have a few bills each year that I cannot pay by electronic transfer of funds and I must only pay by sending a check. So for those few payees, I have found useful the guidance put out by the ABA, pasted in below, on how to safely write checks. Click the link, or google ABA PRACTICE CHECK SAFETY GUIDE.
Key among the recommendations:
— Use a permanent gel pen to write checks (the ink from gel pens permeate the paper and cannot be rinsed off); and
— Fill in all spaces on the paper check completely, so fraudsters cannot rewrite them to change your intended numbers and names.