Switching mid-contract: bring the position, not the history.
Few contractors can wait for every job to finish before they change how they bill. A contract that is already part-billed can move, as long as its starting position moves with it: what has been billed, what the advance has given and taken back, and what retention is held.
By Muhammad Arslan, founder of Mizarah, who kept a UAE joinery's books for thirteen years · 6 minute read · Updated 24 October 2026 · Practical guidance, not tax advice: confirm anything that matters for your business with your tax agent or the Federal Tax Authority.
You do not need to re-enter old claims. Bring the contract's position on the day you switch: work billed to date before VAT and deductions, the advance received and the VAT declared on it, the advance already recovered, the retention held, and whether the old claims took deductions before or after VAT. With those, the next claim recovers only the advance that is left, the contract still stops at 100%, and the old retention's VAT at release follows the method the old claims used.
Five figures carry a contract across.
Take them from your last certificate and your last advance tax invoice, as at the day you switch. The old claims' VAT belongs to the returns for the periods they were issued in, worked out from the old records; it is not declared again.
- Work billed to date, before VAT and before taking off the advance and the retention.
- The advance received, the VAT declared on its tax invoice, and that invoice's number.
- The advance already recovered on the old claims, before VAT.
- The retention held: without VAT if the old claims deducted before VAT, with its VAT if after.
- Which method the old claims used: deductions before VAT or after VAT.
The reference contract, with claim 1 billed before the switch.
Contract 1,000,000 ex-VAT, a 30% advance and 10% retention, with claim 1 (30% of the work) billed in the old system. Its starting position under each method:
| Figure | Before VAT | After VAT |
|---|---|---|
| Work billed to date | 300,000.00 | 300,000.00 |
| Advance received | 300,000.00 | 300,000.00 |
| VAT declared on the advance | 15,000.00 | 15,000.00 |
| Advance already recovered | 90,000.00 | 90,000.00 |
| Retention held | 30,000.00 | 31,500.00 |
| Advance left to recover | 210,000.00 | 210,000.00 |
After VAT the retention held includes its VAT (30,000 + 1,500), because the old claim declared it.
The next claim carries on as if nothing changed.
Claim 2 bills 40% of the work. It recovers its share of the advance from the 210,000 left, and the contract can still bill only the 700,000 not billed yet.
| Line | Before VAT | After VAT |
|---|---|---|
| Work certified | 400,000.00 | 400,000.00 |
| VAT on the work certified | — | 20,000.00 |
| Less advance (30%) | −120,000.00 | −126,000.00 |
| Less retention (10%) | −40,000.00 | −42,000.00 |
| VAT on the net, before VAT | 12,000.00 | — |
| Payable | 252,000.00 | 252,000.00 |
After VAT the claim declares 20,000 − 6,000 = 14,000, naming the old advance tax invoice whose VAT it does not declare again.
The old retention's VAT follows the method it was withheld under.
Before VAT, the 30,000 withheld on claim 1 was never taxed, so its release is a tax invoice for 30,000 plus 1,500 of VAT, declared when you release it.
After VAT, the 31,500 held already had its VAT declared on the old claim, so its release carries none.
| Line | Before VAT | After VAT |
|---|---|---|
| Retention released | 30,000.00 | 31,500.00 |
| VAT declared on the release | 1,500.00 | 0.00 |
| Payable | 31,500.00 | 31,500.00 |
Agree the position before you issue anything new.
Check the five figures against the last certificate the main contractor signed and against the old advance tax invoice. Once the new software has issued a document on the contract, the starting position should not change: every later figure is worked out from it.
In Mizarah this is "Billed before Mizarah" on the project: the as-at date, the claims already issued, the work billed to date, the method the old claims used, the advance received and its VAT with the old invoice number, the advance already recovered and the retention held. It shows what is billed, the advance left to recover and the next claim, and it is frozen once Mizarah issues anything on the contract.
Common questions.
- Do I have to re-enter my old claims?
- No. The starting position carries the contract: work billed to date, the advance received and recovered, the retention held and the old claims' method.
- Will the advance's VAT be declared twice?
- No. It was declared on the old advance tax invoice. Before VAT, the new claims deduct the advance at its net value; after VAT, they deduct it with its VAT and subtract the VAT already declared.
- Do the old claims go into the new VAT return?
- Their VAT belongs to the returns for the periods they were issued in, worked out from the old records. If you switch in the middle of a period, that period's return needs both: the old documents and the new ones.
- What if the old claims mixed the two methods?
- Then the old figures follow neither method. Agree with your tax agent how to correct them before carrying the position across, so the new claims start from figures that are right.
Read next: VAT on progress claims: before or after deductions · Retention on UAE fit-out contracts · Choosing software for a UAE contractor
See your own contract worked out this way.
Put a contract you have already billed through the trial and check the figures against what you invoiced. No card needed, and nothing you enter is deleted when the trial ends.