The mathematical skills of a bookkeeper's job are basic.. It's simple addition, subtraction, multiplication, division, decimals, fractions and percentages, and that's about it. The bookkeeping job applicant must have an ability to know the difference between "money in" and "money out."
Then, the bookkeeper must write it all down every day and balance it every month. Every "money in" transaction must be recorded. Every "money out" transaction must be recorded. There are no known exceptions to this.
That part is not hard.
That part is boring.
That part is absolutely freaking necessary and honesty with accuracy are essential.
The ability to recognize mistakes . . . the ability to admit to and to correct mistakes . . . is fundamental.
Bookkeepers who try to bury the shit in public are feral and need to be neutered.
Knowledge of computers and their uses is required.
Bookkeeping magicians, tricksters, jokers, slackers and slobs need not apply