answer:In the past I’ve written my own “deposit slip” when I didn’t have one. (In fact, it’s the old-fashioned way to do it. Banks at one time did not provide pre-printed deposit slips. You’d go to the bank, use their ‘form’ and fill in your own account number.) Just be very sure to double-check that the account numbers are 1) correct and 2) perfectly plain (so your 1s don’t look like 7s and 7s don’t look like 2s, etc.). Your dad was correct. We have a pretty good track record, we dads. EDIT / Addendum: The other thing that I always do when I’m mailing a check is endorse it “For Deposit Only” (so that no one can intercept it and cash it), and sometimes for a belt-and-suspenders thing, I’ll repeat the account number under that endorsement, before I counter-sign the check.