Which rate to use when the contract is silent

Choose one published source and one date, write both into the next order confirmation, and hold to them until the supplier objects. A central bank reference rate on the invoice date is the most defensible default, because it is published, dated and outside the control of either party.

What a currency gap does to the one-cent tolerance

It turns a convention into an argument. The cent comes from four decimals in a list and two on an invoice, and a conversion adds a third source of imprecision on top: the cent that is rounding and not an overcharge sets out where the original figure comes from and what it covers.

Where the converted price should live

In the working, not in the documents. Keep the list as the supplier sent it and the invoice as it was issued, and hold the conversion in the comparison, so that a later argument about the rate reopens neither document. Reading the list itself is in reading a price list in Excel.

An invoice in one currency against a price list in another

10 November 2026 · Ця сторінка надається англійською мовою.

Kristel Mägi

A price list in euros and an invoice in pounds is ordinary and lawful. The currency gap is not itself a finding. What has to be settled before any line is compared is the rate that converted the goods, and no invoice in either currency is obliged to print it.

Two sheets of ruled paper laid side by side on a drawing board, each with a column of blank boxes, a single coloured pencil line drawn between one box and its neighbour.

Price Double Check sets a forwarded invoice beside the price list it should have been billed on and answers by email with the lines where the two disagree. A currency difference between the documents does not change that arithmetic so much as add a step in front of it, and the step is the one nobody writes down.

The currency on an invoice is the supplier's choice

Under the common system of value added tax the amounts on an invoice may be expressed in any currency, provided the amount of VAT payable is expressed in the national currency of the member state where the supply takes place, converted by the mechanism the directive lays down. That is the whole of the rule. A supplier may price a catalogue in euros and bill a British customer in pounds, and nothing irregular has happened.

So the instinct that something has gone wrong is misplaced. The documents are in order. What has become harder is the comparison, and it has become harder because of three things that are absent rather than wrong.

What neither document carries

The price list often states no currency at all. Of the three price lists in the set this service was validated against, not one named its currency anywhere on the sheet: euros were inferred from the supply contract and from the invoices that followed. A list with no currency against an invoice with one is an assumption waiting to be written down.
The invoice carries no rate. The European standard has a field for the currency of the invoice and a field for the currency VAT is accounted in, and a rule that the second must differ from the first whenever it is given. It has no field for the rate between them, and the Peppol billing specification says as much: the exchange rate is not in the invoice instance, so the conversion is not validated by anything.
Neither document carries the day the rate was taken on. The European Central Bank publishes euro reference rates for 29 currencies at around four in the afternoon, central European time, on working days, and says they are averages of buying and selling rates which do not necessarily reflect the rates at which transactions were made. One working day either side is a real difference in a converted price.

Six checks before a line is compared

Establish the currency of the price list from outside the price list: the contract first, an earlier invoice second, a written answer from the supplier third. Record it beside the file rather than carrying it in your head.
Read the decimal separator per document rather than per country. In that same set the Spanish documents used a point and the Estonian ones a comma, and then one Estonian invoice used a point throughout. A separator inferred from the language of a document is a separator that will be wrong on the document that breaks the pattern.
Agree the rate and its date with the supplier in writing, before the next invoice rather than after it. The clause is one sentence: which published rate, taken on which day, and whether that day is the invoice date, the delivery date or the order date.
Convert the list and leave the invoice alone. The invoice is the document under dispute, so its figures should reach the supplier in the form the supplier printed them, with the converted list price shown beside them as the comparison.
Join on the item code, as always. The currency has no bearing on the key, and descriptions do not survive the journey between the two documents: 335 of 442 lines in the validation set carried a description that did not match its own row in the list.
Set the tolerance after the conversion rather than inheriting it. A list kept to four decimals against an invoice issued to two already earns a tolerance of a cent per unit; a converted list price carries the precision of the rate on top of that, so the cent stops being the right number and has to be argued for.

What counts as a finding and what counts as a query

The division is the one that governs freight. Where no document carries a reference figure there is nothing to judge, and sending an unjudgeable difference out as an overcharge is how a routine loses the person reading it.

What you see	What it is	What to send
The billed price beats the converted list price by more than the tolerance, on a rate and a date both sides have agreed	A price finding	The line, both prices, the rate, its date and the difference in the invoice currency
The billed price beats the converted list price under some plausible rates and not others	A rate query	The line and the range it falls in, and a request for the rate and date the supplier used
Nothing inside or outside the price list states its currency	An absence of basis	No figure at all. A request that the supplier state the currency of the list in writing
The invoice totals in one currency and states its VAT in another	Ordinary and correct	Nothing. That is what the standard asks for when the invoice currency is not the national one

Only the first row is a finding. The middle two are questions with a named recipient, which is better than a false alarm and worse than a figure.

Коротко

Which rate to use when the contract is silent: Choose one published source and one date, write both into the next order confirmation, and hold to them until the supplier objects. A central bank reference rate on the invoice date is the most defensible default, because it is published, dated and outside the control of either party.
What a currency gap does to the one-cent tolerance: It turns a convention into an argument. The cent comes from four decimals in a list and two on an invoice, and a conversion adds a third source of imprecision on top: the cent that is rounding and not an overcharge sets out where the original figure comes from and what it covers.
Where the converted price should live: In the working, not in the documents. Keep the list as the supplier sent it and the invoice as it was issued, and hold the conversion in the comparison, so that a later argument about the rate reopens neither document. Reading the list itself is in reading a price list in Excel.

Forward one invoice and the price list it should have been billed on, together with the line of the contract that says which currency the list is in, and the comparison comes back by email with the differing lines and the arithmetic behind each of them. What a check costs is on the home page.