Silence Is Agreement: Auditing Small Deductions Before They Become a Standing Discount

The slow arithmetic of an unauthorised deduction

A deduction of £45 against a £4,000 invoice rarely provokes a call. It arrives described as a handling charge, a goodwill adjustment or a rebate true-up. The supplier absorbs it because the cost of challenging the sum appears greater than the sum itself. That calculation is rational in isolation and corrosive in aggregate. Twelve such deductions across a year represent £540; across a customer base of thirty similar accounts, the figure is £16,200. The individual credit note is trivial. The pattern is a price cut.

The difficulty is structural. An unauthorised deduction is not a single event but an instalment plan. Each instalment is small enough to accept, and each acceptance makes the next one easier. The customer's accounts payable function records the deduction as settled practice. The supplier's ledger records a slightly reduced margin. Neither party has agreed a new price, yet the commercial relationship now operates as though one exists.

Silence is read as agreement. That is the central risk. A supplier who does not reject a deduction within a defined period leaves the customer with a reasonable belief that the adjustment was accepted. In contract law, conduct can vary terms where the other party relies on it. In practice, the customer's finance team does not need a legal opinion to treat tolerance as permission.

A credit note is not a price agreement

A document described as a credit note is often not a credit note in the strict sense. Under UK VAT rules, a credit note is normally issued by the supplier to reduce the value of a supply. Where a customer sends a document called a credit note, it may in fact be a deduction notice or a debit note raised under a self-billing arrangement. Unless self-billing has been agreed in writing and the customer is authorised to issue documents on the supplier's behalf, the customer cannot unilaterally create a valid VAT credit note.

That distinction matters for two reasons. First, it means the supplier retains control over the VAT treatment of the supply. Second, it exposes the weakness in the customer's position: an accounting adjustment is not the same as a contractual variation. A price change requires consideration or a deed, or at least a clear agreement. A deduction notice signed by nobody and referenced to no purchase order does not meet that standard.

None of this prevents the deduction from being made. It simply means the supplier has grounds to reject it, provided the rejection is timely and documented.

The year-end ledger review: matching every deduction to authority

A year-end review should begin with a single extract: every credit note, debit note and deduction posted against customer invoices during the period. Group the entries by customer and by reason code. Then reconcile each entry against four sources: the original purchase order, the signed contract or terms of business, the delivery note or proof of supply, and any agreed rebate schedule.

Three tests should be applied to each deduction. Is there a purchase order reference that ties the deduction to a specific transaction? Is there signed authorisation from a named individual with authority to vary the contract? Is there a contractual basis, such as a documented rebate, service credit or agreed settlement? If the answer to all three is no, the deduction is unsupported.

Quantify the unsupported total by customer and as a percentage of turnover. A customer whose deductions amount to 1.5 per cent of annual invoiced value is not making occasional adjustments; they are operating a systematic discount. The review should also identify repeat reasons. A 'goodwill adjustment' that appears in four consecutive quarters is not goodwill. It is a recurring charge that has never been agreed.

The output of the review should be a schedule, not a complaint. The schedule lists each unsupported deduction, the invoice it relates to, the amount, the date and the reason given. That schedule becomes the basis for a written rejection and, where appropriate, a re-invoice.

A written policy with a fixed window

The review is of limited value without a standing policy. The policy should state that any credit note or deduction notice lacking a purchase order reference, signed authorisation and a contractual basis will be rejected in writing within fourteen days of receipt. The rejected amount will be re-invoiced immediately. Acceptance of any single deduction does not constitute a waiver of the supplier's right to reject future deductions.

The fourteen-day window should be written into the terms of business and communicated to customers at onboarding. It should also be repeated on the invoice itself, in a single sentence, so that the customer's accounts payable team sees it before the deduction is processed. The policy is not an invitation to litigate small sums. It is a boundary that prevents small sums from becoming a pricing convention.

Where a customer persists in making unsupported deductions, the supplier should escalate through the contractual dispute process. If the re-invoiced amount remains unpaid beyond the agreed terms, statutory late payment rights may apply, including interest and compensation. But the primary objective is not recovery of £45. It is the preservation of the agreed price.

The precedent is the real exposure

Small deductions are rarely worth a standalone argument. They are always worth a policy. The year-end ledger review converts an accumulation of trivial adjustments into a visible number. The written policy converts that number into a boundary. Together they address the instalment-plan nature of the problem: each deduction is small, but the precedent is not. A supplier who rejects unsupported credit notes within a fixed window is not being combative. They are ensuring that silence is no longer read as agreement.