The increase letter and the next price list rarely agree

7 September 2026 · Ця сторінка надається англійською мовою.

Kristel Mägi

A supplier's increase letter announces a percentage. The price list that follows carries the lines, and the two rarely match. Set the old list beside the new one, compare row by row on the item code, and check the first invoice against the list rather than against the letter.

Price Double Check does that comparison on documents forwarded by email, and it is the same work whether a machine does it or you do. What follows is the order to do it in: the checks that find the cause fastest, from the letter itself down to the line where the money actually moved.

The letter is a claim, the list is the fact

An announcement is not a finding. If a supplier writes that prices rise by five per cent from the first of March, then reporting back that prices went up by five per cent tells you nothing you were not told. The letter has already disclosed it.

The finding is the composition. Five per cent across a catalogue is an average, and an average is a shape: some lines move by twelve, some by nothing, one or two move down, and a handful change in a way the letter did not mention at all. That shape is what the supplier did not announce, and it is the only part of the letter worth your morning. What that costs to have produced for you every month is on the home page.

Keep the letter. Store it beside the lists as a document in its own right, dated, with the percentage and the effective date written down. You will need it twice: once to compare against the new list, and once when an invoice arrives dated before the effective date and priced after it.

Six checks, in the order that finds the cause fastest

1. Read the effective date, not the letter date. A letter sent on 20 February for prices effective 1 March gives you nine days and a rule: an order placed on 28 February and delivered on 3 March belongs to one of the two lists, and the answer is written in your terms, not in the letter.
2. Count the rows in both lists. If the new list is shorter, you are not comparing two catalogues, you are comparing a catalogue with an extract. A partial list will manufacture dozens of false discontinuations. Report an item as gone only between two complete catalogues.
3. Join on the item code, never on the description. Across one real set of 442 invoice lines, 335 carried a description that did not match its own price-list row word for word — the same product written two ways by two departments. Codes match, prose does not.
4. Compare the lines that moved against the announced percentage. In the validation set, two consecutive lists differed on sixteen lines out of 177 that carry a code. Sixteen is a number you can read in ten minutes and argue about with a name attached.
5. Look for pack sizes that changed while the price stayed. Four of them sat in that same set, and they are the reason this check exists at all.
6. Then, and only then, check the first invoice under the new list. Not against the letter, and not against the percentage. Against the list.

A smaller pack at the same price is an increase the invoice will not show

This is the check that pays for the other five. Invoices in the validation set print a code, a description, a quantity and a price. They do not print the pack size. The list does. So a bottle that went from 550 to 500 millilitres at an unchanged price is a rise of about ten per cent that is invisible on every invoice you will ever receive for it, and visible only when one list is held against the other.

Four such changes were in one supplier's two lists. None of them appeared in the letter. None of them would have appeared in a spreadsheet built from invoices, because the input the spreadsheet needs was never on an invoice.

Rank by percentage and by novelty, never by euros

A price list has no spend in it. A line that rose 40 per cent and is bought once a year and a line that rose 2 per cent and ships every month are different problems, and until you have the invoices you cannot tell which is which in money. So on a list comparison, sort by percentage and by what is new. Save the euro totals for the invoices, where the quantities live.

What the first invoice is really for

The letter and the list can agree perfectly and the invoice still be wrong. In the acceptance run one line was billed at 13.23 euros against 11.235 in the last list the buyer had been sent — 17.75 per cent over, 47.76 euros on that invoice alone, and enough to take 91 per cent of the margin on the delivery. The cause was not a dishonest increase. The current year's list had simply never been sent, so the buyer was comparing against a document that had quietly expired.

A second pattern is slower and worse. One item was billed at 1.26 euros from March while the list in force said 1.176; the higher figure only appeared in a published list in October. By then it had been paid seven months running and looked like the normal price, because that is what a price becomes when nobody compares. The method for catching it across a run of invoices is in how to check an invoice against a price list.

Forward one invoice and the price list it should have been billed on, together with the increase letter, and the reply names the lines that moved, the ones that moved more than announced, and the ones the letter never mentioned.