Stock as a ledger: why we record movements, not counts

Six kinds of movement

Purchase — into storage, with the unit cost on the line. Transfer — between storage and a unit, or between units. Use — consumed in a clean or a repair, against a unit. Sale — to a tenant, at the selling price, creating an invoice line. Damage — lost or broken, optionally billed at cost. Adjust — the month-end count differs from the computed stock, recorded with a note.

What is computed

Stock anywhere — storage, each unit — is the sum of movements in and out of that place. Value at cost is stock times the cost remembered on the purchase lines. Consumption this month is the sum of use, sale and damage lines dated this month, at cost, and that is what the P&L charges — not what you bought. Why purchases are not expenses.

What a count can't tell you

That 2E's shelf ran out twice this month and the cleaner topped it up from storage both times. That the last bottle sold was sold by Shane on the 9th and invoiced. That a case went missing between the 15th and the 31st. Each of those is a line in the ledger and a line in the audit log, which is why a ledger is also an honesty instrument.

The monthly count still matters

Count storage once a month. Where it differs, record an adjustment with a reason. A ledger that is never reconciled drifts; one that is reconciled monthly is usually within a unit or two, and the adjustments tell you where the leaks are.