Agreeing and invoicing extra work: how to actually get paid for it
Written by Ilias Aarrass6 min read · Published on · Last reviewed on 
In short
You may charge extra for additional work, but only if you warned the client in good time of the need for that price increase, unless they should have understood it themselves.
- In good time means before you carry it out: a message with what is going on, the cost and the delay is enough.
- Put additions and deductions on your invoice as separate lines, with the date of approval.
- The VAT rate on extra work follows the main work, so it is reverse-charged too on a subcontracted job.
- Include an extra-work clause in your terms and send them before or when the assignment is agreed.
Almost every job grows along the way. The client prefers different tiles after all, the pipe behind the wall turns out to be rotten, or an extra room is added halfway. You may charge for that extra work, but in practice that is exactly where money is left on the table: the client thinks it goes without saying, or says afterwards that they never agreed to anything. The law is clear about it, and that clarity works in your favour as long as you do one thing: say in good time that it will cost more. This article shows how to record it, how to invoice extra work and what to put in your terms.
The rule: warn before you start
In a contract for work you may charge extra for additions or changes, but only if you warned the client in good time of the need for that price increase. That is not required if they should have understood it themselves, for example when they pick a more expensive kitchen during the work. Turn it around: anything the client did not choose themselves must be reported before you carry it out.
In good time means: before you carry out the extra work, not on the final invoice. A message explaining what is going on, what it costs extra and how much longer it takes is enough. If you get an approval back, you have your evidence. If that feels too formal for a small change, remember that this is exactly the item that causes arguments afterwards, and that in a dispute you have to show you gave warning.
Three kinds of price agreement, three kinds of extra work
What counts as extra work depends on what you agreed. With a fixed contract price, anything not in the description is extra work. If you work on a time and materials basis at an hourly rate, extra work is simply extra hours, but the client still expects you to flag it when the indicative price is exceeded. With provisional sums, for example an amount reserved for sanitary ware, the difference between the sum and the actual price is settled up.
Put that choice in your quote, not in your head. Describe exactly what is in the price and what is not, and state how you handle extra work: written approval in advance, at which hourly rate, and whether materials are passed on with a mark-up. See writing a quote and passing costs on to your client.
| Agreement | Extra work is | Where it goes wrong |
|---|---|---|
| Fixed contract price | Anything outside the described work | A vague description in the quote |
| Time and materials, hourly rate plus materials | Extra hours and extra materials | No indicative price, so a surprise afterwards |
| Provisional sum for one item | The difference from the actual price | No evidence of the actual purchase price |
Worked example: a bathroom with extra work
- Contract price per the quote
- € 8,500
- Replacing a rotten pipe, reported and approved by email
- € 640
- Tiles dearer than the € 900 provisional sum
- € 1,350, so € 450 more
- Work dropped: no new door
- € 300 less
Result: The final invoice comes to € 9,290 excluding VAT, with the additions and the deduction as separate lines. Because the pipe was approved by email in advance and the tile price follows from the supplier's receipt, there is nothing left to argue about.
Extra work on the invoice
Put extra work on your invoice as separate lines, each with a short description and the date of approval. That makes the invoice checkable and stops a client sitting on the whole bill because they do not recognise one item. Work that was dropped goes underneath in the same style as a deduction.
The VAT rate on extra work follows the work itself. If you do insulation work at 9 per cent and extra insulation is added, that stays at 9 per cent; extra work outside the scheme is 21 per cent. If you work as a subcontractor with reverse-charged VAT, the extra work is reverse-charged too, see reverse-charged VAT in construction and which VAT rate applies.
For larger amounts it is wise not to save extra work up for the final invoice but to bill it in between. Otherwise you finance it yourself, and at the end you risk the discussion about extra work holding up your entire final instalment. If the job runs past 31 December, the extra work performed also counts towards your work in progress.
Putting it in your terms
Include an extra-work clause in your terms and conditions: extra work is confirmed in writing or by message in advance, at the agreed hourly rate, and is invoiced in between. Make sure you send those terms before or when the assignment is agreed; a reference on the back of the final invoice does not work.
If a client still refuses to pay, the ordinary rules apply: first a reminder, then a formal demand with a fourteen-day term, then collection costs and if necessary the courts. See statutory payment terms and collection costs and when a client does not pay. With a message containing the approval you stand considerably stronger in such a process than with a memory of a conversation.
Frequently asked questions
May I charge for extra work without a signature?
Yes, a signature is not required. But you must have warned the client in good time about the higher price, unless they should have understood it themselves. A message with their approval is enough evidence.
What if the client says afterwards that they never agreed?
Then your records decide the outcome. With a message stating the price and a reply approving it, you are in a strong position. Without any trace, it is hard to hold up your extra charge.
Which VAT rate applies to extra work?
The same rate as the work it belongs to. Extra work within a job at 9 per cent stays at 9 per cent, and on a subcontracted job with the reverse charge the extra work is reverse-charged too.
Do I have to settle up work that was dropped?
Yes, if work from the quote is dropped, you deduct it from the price. Put both additions and deductions on your invoice as separate lines; that makes the final settlement immediately clear to the client.
Sources
- Dutch Civil Code Book 7, title 12 on contracting for workOverheid.nl · wetten.overheid.nl
- Drawing up terms and conditions and providing them in timeOverheid.nl · ondernemersplein.overheid.nl
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This article provides general information based on the rules known for 2026 and does not replace personal tax advice. For your specific situation, we're happy to take a look with you.
