Thanks Bullfrog. I'm quite fond of
ut supra - although I suspect my clients would need to have it spelt out as "ut supra" rather than "as above" in the clue!
Although I've rejected my original idea using "debtors" to clue "A/R", I'd be grateful to know whether any of you think that an acceptable reference anyway. I was really surprised to find that none (literally, none) of my colleagues claimed to have come across "A/R" in a set of accounts - and I was pretty convinced that (i) I've seen it in most of the accounts I've looked at in the course of my work, and (ii) "accounts receivable" is in reasonably common usage anyway.