Odds or evens.

[Workingman]

(9 is a good figure. If you ever have a discrepancy which divides by 9, then you've reversed a figure somewhere in your listings. For example, if you have a difference of 27 in your reconciliation, well, that divides by 9. What you'll find is that you've written 63 somewhere instead of 36, or you've written 58 instead of 85 .... works every time! )

What on Earth are you blathering on about? Neither 9 nor 3 goes into 58 or 85.

Miss, can I have a couple of what he's drinking, please?

[Diflower]

Well as someone whose first job was as a trainee bookkeeper I understand it
A reversed figure is the first thing to look for, as it's a common and simple mistake.
It's if the discrepancy will divide by 9 WM

So, if column a adds up to 1,526 but columns b, c & d (which should add up to column a) come to 1,553; somewhere you're out by 27.
The first thing you look at is whether that difference is divisible by 9, which it is.
Then you look down your columns of figures for one that could easily be entered wrongly, ie by writing 158 instead of 185 - or, when adding up on a calculator, entering the reversed figure by mistake. It happens a lot
And the difference between 185 and 158 is 27, so you've found your mistake

It sounds odd until you're used to it, but when you're doing calculations etc all day long, your brain would automatically check for it.

[TheOstrich]

Absolutely spot on, Di.

(Although I once spent half a day looking at columns of figures because I had an overall discrepancy of £9, checking all the £12's and £21's and the £43's and the £34's were accurate, without any joy - only to discover later I'd made two simple addition errors, £10 one way and £1 the other way .....)