AFTER THE APPLICATION · YEAR-END CLOSE
Reporting WBSO actuals: what do you have to submit before 31 March?
The WBSO actuals report closes the calendar year: you compare what RVO has granted with what was actually carried out and report the realised R&D hours and, where applicable, the realised costs and expenditures. RVO officially calls this the reporting of the actuals.
BY PETER KLAREN · LAST CHECKED SEPTEMBER 2026 · SOURCE: WBSO GUIDE 2026 (RVO)
WBSO 2026: report the actuals by 31 March 2027 at the latest
Did you use WBSO in 2026? Then you report the realised R&D hours and any actual costs and expenditures no later than 31 March 2027 to RVO. The report must be made within three months after the end of the calendar year.
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Reporting WBSO actuals at a glance
| Situation | What to report? | Deadline |
|---|---|---|
| Employer – flat rate | realised R&D hours | 31 March next year |
| Employer – actual costs | hours + realised costs and expenditures | 31 March next year |
| Self-employed ≥ 500 R&D hours | no report needed | — |
| Self-employed < 500 R&D hours | report realised R&D hours | 31 March next year |
| R&D declaration received only after year-end | hours + any costs | within 3 months after date of declaration |
| Business ceases | hours + any costs | within 1 month after cessation |
What is the WBSO report of the actuals?
After the end of the calendar year you compare what RVO has granted with what your company actually realised in R&D. You then report the actually realised R&D hours and, with the choice for actual costs and expenditures, also the actually realised amounts.
The actuals report is thus the close of the WBSO year. RVO uses the official term reporting of the actuals; in practice one also speaks of the actuals report or reporting realised hours.
Reporting WBSO actuals for employers
Every R&D withholding party must make a report. That applies even when a project was ultimately not carried out at all.
Did you choose the flat rate?
Then you report only the realised R&D hours.
Did you choose actual costs?
Then you additionally report the actually realised and paid R&D costs and R&D expenditures.
More about that choice: WBSO costs and expenditures.
Reporting WBSO actuals for self-employed professionals
| Realised R&D hours | What do you have to do? |
|---|---|
| 500 hours or more | No report needed. Your hours records must of course still demonstrate that the 500-hour requirement is met. |
| Fewer than 500 hours | Report. RVO withdraws the R&D declaration and the previously granted R&D deduction cannot be applied in the income tax return. |
If a self-employed professional makes no report, RVO assumes that at least 500 R&D hours were realised. That does not release you not from the record obligation: in an audit you must still be able to demonstrate those hours with your hours records.
Self-employed with staff?
For your own R&D deduction the 500-hour rule applies. For your staff’s WBSO the rules for employers additionally apply, including the mandatory annual actuals report. You then have two different roles.
Multiple R&D declarations? One report
Employers make one report of the actuals covering the whole calendar year, even when multiple R&D declarations were received. You report the total number of realised R&D hours and, if you chose actual costs and expenditures, also the realised costs and expenditures.
If you have multiple declarations, RVO advises calculating the totals over the calendar year before submitting. So there is no separate report per declaration.
What if you realise less or more WBSO than granted?
| Realisation | Consequence |
|---|---|
| Project not carried out at all | Correction of the granted benefit |
| Fewer hours realised | Partial correction possible |
| Fewer actual costs or expenditures | Partial correction possible |
| More hours realised than granted | No extra WBSO |
| More costs realised than granted | No extra benefit for the excess |
With less realisation RVO issues one correction amount for the R&D declarations of the calendar year. Realising more than granted does not lead to a higher WBSO decision — the granted amount is a maximum, not an indicative amount.
What is a corrected R&D declaration?
When the realised R&D hours and/or actual costs and expenditures are lower than granted, RVO can issue a corrected R&D declaration . It recalculates how much R&D payment reduction your company is ultimately entitled to.
Too much offset
If you have already offset more WBSO than remains according to the correction, the difference must be repaid via the payroll taxes.
Too little offset
If you have offset less than you are still entitled to according to the correction, you can under conditions still apply the payment reduction.
Do you disagree with a correction? See objecting to a WBSO decision.
May you shift WBSO hours between projects?
Yes. Within the same calendar year you can under conditions shift granted but non-realised hours to other already approved R&D projects — also across different R&D declarations. The same applies to granted amounts of costs and expenditures.
Important limits: you can only shift within already approved projects and within granted hours and amounts. And: hours remain hours, euros remain euros — hours and amounts may not be exchanged for each other.
What do you need for the WBSO actuals report?
| Needed | When? |
|---|---|
| R&D declaration(s) | always |
| Hours records | always |
| Total realised R&D hours | always |
| Cost and expenditure records | with actual costs |
| Invoices and proof of payment | with actual costs |
| eHerkenning level 3 | for submission |
| Chain mandate | if an intermediary submits |
Reporting WBSO actuals in 5 steps
- 1Close the recordsClose the hours, project and any cost records over the calendar year.
- 2Add up the hoursAdd up the total number of realised R&D hours across all approved projects and declarations.
- 3Determine costs and expendituresOnly with actual costs: determine which amounts were actually realised and paid.
- 4Compare with the decisionPut the realisation next to the granted amount and assess whether a correction is to be expected.
- 5Submit the reportSubmit the report via RVO’s eLoket with eHerkenning level 3.
Exceptions to the 31 March deadline
31 March is the main rule, but does not always apply.
| Situation | Deadline |
|---|---|
| Normal situation | 31 March of the following calendar year |
| Declaration received only after calendar year-end | Within 3 months after date of R&D declaration |
| Business ceased or bankruptcy | Within 1 month |
| Withholding obligation ends | Within 1 month |
See also the complete WBSO deadline calendar.
What happens if you report the WBSO actuals too late?
Reporting late
A late report can lead to a fine. If you moreover realised less R&D than granted, a corrected R&D declaration additionally follows.
Not reporting at all
If an employer does not make the mandatory report at all, RVO can set the realised hours and any costs and expenditures at nil. That leads to a full correction and a fine.
Also prepare for a possible RVO audit — the actuals report and the underlying records must connect.
Frequently asked questions about the WBSO actuals report
When do I have to report the WBSO actuals?
Do I always have to report the actuals?
I have multiple R&D declarations. Do I have to make multiple reports?
What do I report with the flat rate?
What do I report with actual costs and expenditures?
What if I realised fewer hours?
What if I realised more hours than granted?
Can I shift hours between projects?
What if I am late reporting?
What happens if a project did not start?
Practical tip: compare granted and realised hours per project. Structural under- or overestimates provide a good basis for a more realistic WBSO budget for the next year.
Is your WBSO actuals report correct?
We check your realised hours, costs and expenditures and assess in advance whether a correction is to be expected — before you submit.
SOURCES AND SUBSTANTIVE REVIEW
Reviewed by Peter Klaren, WBSO specialist since 2004. Last substantively updated: 21 September 2026.