Restaurant bookkeeping as double-entry data: prime cost, tip liabilities and delivery gross-up

The article treats a restaurant's books as structured data, identifying a few rules that carry most of the accounting logic. Prime cost is defined as food cost plus beverage cost plus all labor, divided by sales. Card tips and sales tax are recorded as liabilities that should trend back toward zero once paid out, and delivery app payouts are net figures that must be grossed up into sales and expense lines. The author, who builds the ZeraBooks AI-native general ledger, supplies Python examples using Decimal arithmetic, a balance check on each entry, and a sample card deposit that splits revenue, sales tax and tips. The piece argues that persistent residuals in tip or tax liability accounts signal data errors worth catching early, and that a ledger's handling of restaurant books is a useful test of its data model.