Where billing discrepancies hide in discounts, tiers and year-end rebates
Checking the unit price is necessary but rarely sufficient. The costliest discrepancies often sit in the discount mechanisms and in ancillary costs.
Beyond the unit price
The unit price is the first thing people check and the most visible. But a framework agreement contains other financial clauses that are harder to control by hand, because they depend on volumes, periods and calculation bases. The price schedule (BPU) sets the starting tariff; discounts, tiers, year-end rebates and ancillary costs determine the price actually paid.
A tiered discount applies when purchases cross a threshold. In principle it appears on the invoice, and errors come in three kinds: the threshold is reached without the discount being triggered, the discount covers only part of the items concerned, or the tier is assessed over the wrong period.
Two details of the clause change everything. In a retroactive scale, crossing a threshold earns the higher discount on all purchases of the period; in a non-retroactive scale, only purchases beyond the threshold benefit. The scope of the threshold matters as much as its amount: quantity per line, amount per order or cumulative volume over the quarter. A supplier that assesses the threshold order by order when the contract provides for it cumulatively deprives the buyer of discounts that were negotiated.
Year-end rebates are won on the base
Year-end rebates are calculated after the fact, often by the supplier itself. The rate is read from the contract; the base makes the difference. You need to know which purchases count, whether you start from the amount before or after other discounts, whether credit notes are deducted, whether off-contract items are included. A badly defined base reduces the rebate without anyone noticing.
Take a contract that provides for a 2% rebate on all net purchases excluding VAT for the year, shipping excluded, off-schedule items included. The supplier calculates the rebate only on the items of the price schedule.
| Item | Supplier | Contract |
|---|---|---|
| Purchases of price-schedule items | €900,000 | €900,000 |
| Purchases outside the schedule | excluded | €240,000 |
| Rebate base | €900,000 | €1,140,000 |
| Rebate at 2% | €18,000 | €22,800 |
| Discrepancy to recover for the year | €4,800 |
The rate is right and the calculation exact: only the base differs. Repeated every year over five years, the same discrepancy represents €24,000 for a single supplier. For each rebate, the reflex is to rebuild the base from the invoices of the period and compare the result with the amount paid.
Ancillary costs and free shipping
Shipping charged despite a free-shipping threshold, an unplanned fuel surcharge, packaging or handling fees added: these lines are hard to tell apart from one invoice to the next, yet the contract states precisely what can be billed on top. A fuel surcharge is only due if it is provided for, with its formula. Small-order fees only apply below a threshold set in the contract. Price increases, for their part, fall under price indexation clauses.
A contract provides for example for free shipping from €500 excluding VAT per order. The supplier bills €45 of shipping on orders that cross this threshold, because its system assesses the threshold including VAT, or line by line, rather than on the order.
| Order | Amount excl. VAT | Shipping billed | Shipping due |
|---|---|---|---|
| Order A | €420 | €45 | €45 |
| Order B | €515 | €45 | €0 |
| Order C | €980 | €45 | €0 |
Two orders out of three are billed wrongly, a €90 discrepancy. With several dozen orders a month at the same supplier, the annual total becomes significant and appears again in every year of the recoverable period (five years between traders).
A reading grid for each clause
Faced with a discount clause, six points are enough to know what to check:
- the rate and the threshold from which it applies;
- the base: which purchases, before or after discounts, credit notes deducted or not;
- the period: calendar year, financial year, rolling period;
- whether the tier is retroactive or not;
- the effective date of each amendment that changes these terms;
- the method of payment (credit note or transfer) and its due date.
Items bought with no negotiated terms at all are a case of their own, covered in off-contract purchasing.
Frequently asked questions
What is the difference between an invoice discount and a year-end rebate?
An invoice discount is earned on the date of sale and appears directly on the invoice. A year-end rebate (RFA in French contracts) is calculated afterwards, on all purchases of a period, then paid by credit note or transfer. The first is checked line by line, the second has to be reconstructed.
How do I know whether a year-end rebate was calculated correctly?
You rebuild the base from the invoices and credit notes of the period, apply the rate and tiers set in the contract, then compare the result with the amount actually paid. The supplier calculation statement, when there is one, is a starting point.
Is a tier reached during the year retroactive?
It depends on the clause. A retroactive tier applies the higher rate to all purchases of the period as soon as the threshold is crossed; a non-retroactive tier applies it only to later purchases. It is one of the clauses most often misapplied, because it was not read precisely.
