A till that reconciles with the books every night

A point of sale has one quality test, and it is run every evening by whoever counts the drawer. The sales total in the system and the money in the till either agree, or someone spends an hour finding out why. A till that reconciles first time, most nights, is not luck - it is a set of specific design decisions.

Every sale posts, immediately and completely

A retail sale is at least three facts: revenue, the movement of goods out of stock at cost, and the receipt of money into a specific cash box. If any of them is deferred - posted by a nightly job, or left for the accountant to summarise - then the day in the system is a partial record and the reconciliation is against an incomplete number.

The relevant detail is that these must post together or not at all. A sale that recorded revenue but failed to record the cash receipt leaves a drawer that is over by exactly that amount, and nothing in the system pointing at the cause.

The cash box is a real account, not a label

Each till is its own account with its own balance, opened and closed by a named person. Two cashiers sharing one cash box cannot be reconciled separately, so a difference belongs to both of them, which in practice means it belongs to neither.

Shift handover matters for the same reason. Counting at handover converts a day-long mystery into a shift-long one, and a difference found within a shift is usually still explainable.

Returns and refunds are where the money leaks

A return takes goods back and may take money out. Those are separate decisions: a customer may be refunded in cash, or credited against their account, and the two have different effects on the drawer. Treating them as one is how a till is short at the end of the day with no transaction to point to.

A refund is also the most abusable transaction in retail, which is an argument for it needing an authority level rather than a button anyone can press.

Decide what happens when the network drops

A shop cannot stop selling because a connection did. But an offline till is a second source of truth for as long as it is offline, and the reconciliation afterwards is only as good as the rules you set in advance: which documents may be issued offline, what numbering they use so two tills cannot mint the same receipt number, and what happens to a sale that was taken offline for goods that sold out online in the meantime.

The honest version of this decision is sometimes to refuse: a business that cannot tolerate duplicate numbering may prefer a till that stops. What matters is that it is a decision, taken while nothing is broken.

What to check this week

• Pick three days at random and reconcile each till. If differences are routine, they are not differences - they are a design gap.

• Look at the cash box balances in the ledger. A till account that never returns to its opening float is accumulating something.

• Count the refunds given last month and who authorised them. Not as an accusation, as a measurement.