A table of four asks to split the check. It sounds like the simplest request in hospitality, and it's the one most likely to expose a weak point-of-sale system — because "split" means at least three different things, and each one breaks differently.
Three kinds of split
Even split. Divide the total by the number of guests. $86.40 across four is $21.60 each. Easy — until the total doesn't divide.
Item split. Each guest pays for what they ordered, plus their share of anything shared. This is the one guests actually want, and the one that shows whether the system knows what "their share" means.
Split tender. One check, several payments — part on one card, part on another, the rest in cash. Common at the end of a birthday dinner, and where tips go missing.
A good system handles all three. Plenty of systems handle the first and approximate the others.
The missing cent
Divide $10.00 three ways and you get $3.33, $3.33 and $3.33 — which comes to $9.99. A cent has vanished.
Somebody has to pay $3.34. That's obvious written down and surprisingly easy to get wrong in software, particularly once a discount is involved: a percentage taken off each part separately doesn't always add up to the same percentage taken off the whole. Get it wrong and the check doesn't balance, the drawer is a few cents out at close, and someone spends ten minutes looking for money that was never lost.
It's a small thing. It's also exactly the kind of small thing that erodes trust in the end-of-night numbers — and a system that drifts a cent on odd splits tends to drift elsewhere too.
It's a real enough problem that the Sonorch register, for shops running a cash discount, recalculates the discount from the running total of cash after every cash payment on a split check, rather than adding up each payment's share. Adding them up drifts by a cent on odd splits — and the customer can see it.
What to test: split a $10.00 check three ways, then split a check carrying a 15% discount four ways. The parts should add up to the total exactly, every time.
Shared items, and the tax on them
The starter everyone picked at, the bottle of wine, the dessert with four spoons.
An item split has to let you divide one line between guests, and when it does, the tax and any service charge on that line have to follow. The failure here is usually silent: the shared item lands on one guest, who pays for the whole table's calamari and says nothing until they're home.
What to test: put one shared item on a check, split it between two guests, and confirm each guest's part carries half the item and half its tax.
The tip on the wrong card
This is the one that causes real arguments.
With a split tender, a guest writes a tip on their card slip. Which payment does that tip belong to? If the system attaches it to the first card run rather than the card the guest actually tipped on, your records say one person tipped twenty dollars and another tipped nothing. If a guest disputes a charge later, the amounts won't match what they signed.
It matters to your staff as well. If tips are paid out from card records, a tip filed against the wrong payment can end up on the wrong server's shift.
What to test: run a two-card split, tip only on the second card, and check which payment the tip is recorded against.
Voids after a split
A guest changes their mind about dessert after the check has already been divided. Voiding an item from one part of a split should adjust that part — not the whole check, and not leave a stranded charge on the other half. Some systems make you undo the split, void, and split again, which is how mistakes get made at the busiest moment of the night.
Test it on a quiet afternoon
None of these are exotic. Every one of them happens on an ordinary Friday. The only question is whether you find out on a quiet Tuesday with a test check, or at nine o'clock with a table of eight watching.
Half an hour with a handful of fake checks will tell you more about a point-of-sale system than any sales demo. Try the odd split, the shared item, the two-card tip and the void, and see whether the numbers still add up.
If you're comparing systems, run these four tests on every one you're considering — ours included. And the other monthly cost of the till — what card processing really costs you — is worked through in what a free POS actually costs; the arithmetic is the same for a restaurant.