Because it is small enough to feel unimportant. Receipts gather in an envelope, the count happens twice a year, and the difference is written off without anyone knowing what it was.
Petty cash is a float held by a named person, spent against receipted lines, topped up to a set limit, and countable at any moment.
Each float has a holder and a limit. Spend is recorded against a receipt and coded like any expense; a top-up restores the float, so the expected balance is always known.
A count comes up twelve pounds short. The register shows every line since the last count, so the gap narrows to a week rather than a year, and the write-off has a date and a reason.
It will not stop cash going missing. It makes the gap small, recent and attributable, which is most of what control over cash really means.
Spend posts to the ledger and the cost centre like any expense, top-ups post against the bank account, and the float balance sits on the balance sheet.
Yes, one per holder or site, each counted separately.
Above your threshold, yes. Below it, a description will do.
Whoever your approval rule names, and the top-up is recorded against them.
Fourteen days, every module, no card. Or half an hour with someone who will run it on your own records and tell you where it does not help.