An interim invoice is a payment while the work is running. It closes nothing off — the final invoice offsets it later.
Anyone who builds for months and only sees money at the end is financing their client. That is why interim invoices are the normal case in construction, not the exception.
Issuing an interim invoice
Open the quote or the order confirmation and choose Create as a related document → Interim invoice. From an interim invoice you later get another interim invoice, a partial final invoice or the final invoice.
The dialog has the Cumulative tick box. It decides how the arithmetic works, and both ways are permitted:
| Way | What is on the document |
|---|---|
| Individually | Only the work of this period. The second interim invoice knows nothing of the first. |
| Cumulative | All work performed so far, less all earlier interim invoices. The document shows the state of the whole building project. |
Cumulative is what public clients and the VOB/B (the German construction contract procedures; in other countries the local construction contract law applies) expect. Individually is simpler and perfectly fine for small jobs. Do not switch part-way through a building project — none of the invoices will add up afterwards.
If the project is based on a tender, the line items carried over show the same Bidder details as the order confirmation and invoice already do — such as “Brand: …”. How these details come about is explained under Writing a quote.
The final invoice
It bills what was performed in total and, in the totals block under Interim invoices already issued, deducts what has already been paid. What remains is the amount payable.
Check this line document by document. If one interim invoice is missing there, you are asking for money twice; if one too many is listed, you are giving it away. After finalizing, both can only be repaired by canceling.
A partial final invoice settles a completed construction phase for good while the rest carries on.
The retention
In the totals block of the final invoice: type Performance or Defects liability, plus a due date. The amount is deducted from the amount payable and stays outstanding — it is not paid, it is retained.
Set the due date realistically. A defects liability security often runs for five years; without a date, in three years nobody will know when you are allowed to collect the money.
What is not possible today
The DATEV export leaves interim and final invoices out — as it does mixed tax cases and foreign currency. Agree with your tax adviser how these documents reach them. The export exists only for businesses in Germany anyway.