Splitting a bill by item instead of evenly
An even split is faster. An itemised split is fairer. Most of the argument about which to use is really an argument about whether the difference is big enough to bother with — so here is how to tell, and how to do the itemised version without getting it subtly wrong.
When it is worth it
Work out the largest gap between two people's orders. If it is under about a tenth of the bill, split evenly — you will spend longer being fair than the fairness is worth.
Above that, itemise. The usual triggers are alcohol (a table where half are drinking and half are not can differ by a factor of two), one much more expensive main, and a set of small shared plates ordered by some of the table rather than all of it.
Shared dishes
The part people get wrong. A bottle of wine between four is not a quarter each unless all four drank equally, and the starters everybody picked at are not the same as the starters three people picked at.
The usable rule is to split each shared thing between the people who actually had it, not between everybody at the table. It sounds like more work and is usually less, because most shared dishes have an obvious set of takers.
platy24 lets several people claim the same line, and divides it between exactly those people. If two of you shared a starter, it is half each; if three did, a third each — and nobody has to compute the thirds.
Rounds
Rounds are a split that has been spread over time. They are fine while the rounds are equal and stop being fine the moment somebody leaves early or somebody's round happens to include two cocktails and a whisky.
If a night has turned into rounds, the simplest recovery is to stop treating them as rounds and enter each round as an expense with its own payer. The balance then works itself out and nobody has to remember whose turn it was.
The leftover cents
Divide 10.00 between three people and you get 3.33 each, which comes to 9.99. Somebody has to pay the extra cent, and any system that does not decide who is quietly losing money somewhere.
It matters more than it looks because it happens on every line. A twenty-line receipt split three ways produces up to twenty stray cents, and if they are dropped rather than assigned the total no longer matches the bill — which is the moment somebody stops trusting the numbers.
platy24 works entirely in whole cents and hands the remainder to specific people deterministically, so the parts always add back up to the total exactly. Not approximately: exactly.
Somebody left early
The most common way an itemised split goes wrong is not arithmetic, it is somebody putting cash on the table for roughly their share and leaving before the bill arrived. What they left is almost never what they owed.
Treat it as a payment rather than as a discount: enter their items as normal, then record what they handed over. The difference is either still owed to whoever covered it or is change the table owes them, and either way it is visible instead of quietly absorbed by whoever paid the card.
What to do about the things nobody claims
There is always a line nobody remembers ordering. Leaving it unclaimed is not neutral — it means that money is in nobody's balance, so the person who paid is silently out of pocket for it.
Decide it explicitly: either somebody takes it, or it gets divided between everybody. platy24 shows unclaimed lines rather than hiding them, tells you how much they come to, and offers to spread the remainder across the table in one tap.