Quick answer
Compare the invoiced price with the most recent agreed price for the same product, pack size and tax basis. Separate a genuine price increase from a changed pack, substitution, discount expiry or delivery fee. Ask the supplier for the effective date and affected lines, then update your buying reference once the change is understood.
Start with a small price reference
Choose the purchases that matter most to your shop rather than attempting to monitor every small item immediately. Record supplier code, pack format, agreed unit price, quote date and any expiry date. Keep the confirmation itself. A remembered price from last spring is a weak basis for a current dispute.
A retailer might begin with its regularly reordered core lines; a café might start with coffee, milk, packaging and bought-in food. This is a purchasing check, not a recommendation to raise selling prices automatically. First establish what you are being charged and what agreement applies.
Normalise the comparison
Suppose a case used to contain twelve bottles for an illustrative £18, but the new case contains ten for £17. The case price has fallen, yet the bottle price has risen from £1.50 to £1.70. That is a £0.20 increase per bottle, or about 13.3%. The example shows why comparing only invoice totals can miss a change.
Check delivery charges, deposits, surcharges and discounts separately. Keep the same VAT basis on both sides, asking your bookkeeper if you are unsure. A discount disappearing at a quantity threshold is different from the supplier changing its basic price.
| Previous case | New case | |
|---|---|---|
| Units per case | 12 | 10 |
| Case price | £18 | £17 |
| Price per bottle | £1.50 | £1.70 |
Ask whether it is an error or an agreed change
Send the invoice line and the relevant quotation or price confirmation. Ask the supplier to explain the change, including its effective date and whether it applies to orders already accepted. Avoid assuming that every unexpected increase is unlawful or that an old quotation remains valid forever.
The Small Business Commissioner advises making commercial agreements clear in writing. For repeat buying, your own practical safeguard is to retain the price confirmation with its scope and validity, then ask for a fresh quote when either becomes uncertain.
Invoice [number], line [code], shows [price and unit]. Our latest written confirmation dated [date] shows [previous price and unit]. Please confirm whether this is an error, a pack/specification change or a new price, and the date from which the change applies. Please also send the current price list for the affected lines.
Further reading: Small Business Commissioner: contract guide
Update the people who order and receive
Once clarified, record the decision in the buying reference, including any temporary exception or negotiated end date. Tell the person placing the next order; otherwise the same query will be raised on every delivery. Keep old confirmations rather than overwriting the history.
If you compare alternatives, use the same specification and delivered quantity. A lower quoted unit price may involve a larger minimum, longer lead time or different quality. Choose the next action based on the complete offer, and verify any claimed saving against an actual order rather than a sales conversation.
Unpickle helps preserve invoice and delivery records for your checks. It does not negotiate prices or automatically audit supplier price changes for you. Keep invoice details beside the delivery.