Cooking before the bill is paid
A bar tab means food starts before money changes hands. That is easy to say and awkward to build: the kitchen needs the order now, and the accounts must not see a penny until somebody actually pays.
Ring four pints and a burger onto a tab and the burger should start cooking. Nobody in a bar waits for the bill to be settled before the kitchen hears about it. But a till that sends unpaid food to the pass has to answer a harder question than it looks: what is that order, exactly, before anyone has paid for it?
Two rules that pull against each other
The kitchen must have the ticket now. And an unpaid tab must not count as revenue — not in today's takings, not in the VAT figure, not in the vendor's settlement. Systems get this wrong in both directions: some hold the food back until payment, which is useless in a bar; others create a real order at park time and then have to unpick it if the tab is discarded, which is how a night's sales total ends up disagreeing with the cash in the drawer.
A ticket with no order behind it
The answer we settled on is that a parked tab creates a kitchen ticket and nothing else. It has no order, no total and no line in any report, because it is not a sale yet — it is a list of food. The revenue story is intact by construction rather than by a rule somebody has to remember: there is no money row to accidentally count.
When the tab is finally paid, the sale that gets recorded stamps itself onto the ticket the chef has been working from. The board shows one ticket, not two. Whatever state it was in — half the lines ticked, already called ready — carries straight through, because it is the same piece of paper it always was. The kitchen never learns that anything happened.
Adding a round prints the round, not the tab
The other half is what happens when the table orders again. Reprinting the whole tab is how the same burger gets cooked twice, so a re-parked tab prints only the difference — the two pints and the extra chips, marked as an addition. Take something off and nothing prints at all, because paper cannot be un-printed and the screen already shows the corrected list.
All of this sits behind one venue switch, because plenty of counters do not want it: a market stall where everything is paid for as it is ordered has no use for food that starts early. With it off, the kitchen hears nothing until the tab is paid, and the till says which of the two worlds it is in as you park.