My invoice total doesn't match my orders

Three things explain nearly every mismatch. Check them in this order.

Which period does the invoice cover?

A monthly invoice covers orders delivered in that month, not orders placed in it. An order placed on the 30th and delivered on the 2nd belongs to the following month's invoice, and the total you counted from your own records will be short by exactly that order.

Open the invoice and read its line items: each order line names the car, the stage, the number plate where one was recorded, and the delivery date, so a line can be matched to a job at a glance. Compare against your Orders list filtered by delivery date, not order date.

Is the difference VAT?

The invoice total includes VAT (value added tax) where it applies; the prices you see while ordering are shown excluding it. If your total is out by a consistent percentage, that is what you are looking at.

Whether VAT is charged depends on your country and your VAT number. See Which currency am I charged in? for how the money side is decided.

Are you counting credit purchases as orders?

Buying credits and spending credits are two different money events. The credit bundle you bought is invoiced when you buy it; the orders you then place with those credits cost you nothing further. Counting both double-counts the work.

A monthly invoice only ever contains orders billed on invoice — never orders you paid for with credits, and never the credit bundles themselves.

The line items are right but the total still differs

Check for a discount or a credit note on the invoice. A supplier can apply a per-dealer discount, which shows as a reduced line price rather than a separate line, and a credit note from a refunded order reduces the balance without removing the original line.

It is still wrong

Open a support ticket with the invoice number and the amount you expected. An invoice is never edited after it is issued — a genuine error is corrected with a credit note, which keeps both documents intact and auditable.

When the error was the VAT itself — tax charged on a sale that should have carried none, or at the wrong rate — the correction arrives as three documents: the original invoice, a credit note reversing it in full, and a reissued invoice with the right figures. The difference is refunded to your payment method automatically at the same moment. See A credit note and a new invoice appeared — what happened? for how to read and file the set.