Have my WBSO realisation reviewed Help with reporting realisation
BY PETER KLAREN · LAST REVIEWED SEPTEMBER 2026 · SOURCE: WBSO GUIDE 2026 (RVO)
WBSO 2026: report realisation no later than 31 March 2027
If you used WBSO in 2026, report the R&D hours realised and any actual costs and expenditures to RVO no later than 31 March 2027. The statement must be submitted within three months after the end of the calendar year.
ON THIS PAGE
At a glance What is the statement? For employers For self-employed professionals Multiple S&O-verklaringen Less or more realised Corrective S&O-verklaring Reallocating hours and euros What do you need? Report in 5 steps Exceptions to 31 March Late or no report Frequently asked questions
Reporting WBSO realisation at a glance
| Situation | What to report? | Deadline |
|---|---|---|
| Employer – fixed amount | R&D hours realised | 31 March of the following year |
| Employer – actual costs | hours + realised costs and expenditures | 31 March of the following year |
| Self-employed professional ≥ 500 R&D hours | no statement required | — |
| Self-employed professional < 500 R&D hours | report R&D hours realised | 31 March of the following year |
| S&O-verklaring 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 statement of realisation?
After the end of the calendar year, you compare what RVO awarded with what your company actually realised in R&D. You then report the R&D hours actually realised and, if you chose actual costs and expenditures, the amounts actually realised.
The statement of realisation is therefore the closing step of the WBSO year. RVO's official term is mededeling van de realisatie; in practice this is also referred to as the realisation report or reporting realised hours.
Reporting WBSO realisation for employers
Every S&O withholding agent must submit a statement. This also applies if a project was ultimately not carried out at all.
Did you choose the fixed amount?
Then you report only the R&D hours realised.
Did you choose actual costs?
Then you also report the S&O costs and S&O expenditures actually realised and paid.
More about that choice: WBSO costs and expenditures.
Reporting WBSO realisation for self-employed professionals
| R&D hours realised | What must you do? |
|---|---|
| 500 hours or more | No statement required. Your hours registration must of course still demonstrate that the 500-hour requirement was met. |
| Fewer than 500 hours | Report them. RVO withdraws the S&O-verklaring and the S&O deduction previously awarded cannot be applied in the income tax return. |
If a self-employed professional does not submit a statement, RVO assumes that at least 500 R&D hours were realised. This does not remove the record-keeping obligation: during an audit you must still be able to demonstrate those hours through your hours registration.
Self-employed and employees?
For your own S&O deduction, the 500-hour rule applies. For WBSO relating to your employees, the employer rules also apply, including the mandatory annual statement of realisation. You therefore have two different roles.
Multiple S&O-verklaringen? One statement
Employers submit one statement of realisation for the entire calendar year, even if several S&O-verklaringen were received. You report the total number of R&D hours realised and, if you chose actual costs and expenditures, the costs and expenditures realised.
If you have several declarations, RVO advises calculating the calendar-year totals together before submission. There is therefore no separate statement per declaration.
What if you realise less or more WBSO than awarded?
| Realisation | Consequence |
|---|---|
| Project not carried out at all | Correction of the awarded benefit |
| Fewer hours realised | Partial correction possible |
| Fewer actual costs or expenditures | Partial correction possible |
| More hours realised than awarded | No additional WBSO |
| More costs realised than awarded | No additional benefit for the excess |
If realisation is lower, RVO issues one correction amount for the S&O-verklaringen for the calendar year. Realising more than awarded does not lead to a higher WBSO decision — the awarded amount is a maximum, not a target.
What is a corrective S&O-verklaring?
If the R&D hours and/or actual costs and expenditures realised are lower than awarded, RVO may issue a corrective S&O-verklaring. This recalculates the S&O payroll tax reduction to which your company is ultimately entitled.
Too much offset
If you have already offset more WBSO than remains according to the correction, the difference must be repaid through payroll taxes.
Too little offset
If you offset less than you are still entitled to according to the correction, you may under certain conditions still apply the payroll tax reduction.
Disagree with a correction? See objecting to a WBSO decision.
Can you reallocate WBSO hours between projects?
Yes. Within the same calendar year, under certain conditions you can move awarded but unrealised hours to other already approved R&D projects — including across different S&O-verklaringen. The same applies to awarded amounts for costs and expenditures.
Important limits: you can only reallocate within projects already approved and within awarded hours and amounts. And hours remain hours, euros remain euros — hours and amounts cannot be exchanged with each other.
What do you need for the WBSO statement of realisation?
| Required | When? |
|---|---|
| S&O-verklaring(en) | always |
| Hours registration | always |
| Total R&D hours realised | always |
| Records of costs and expenditures | with actual costs |
| Invoices and proof of payment | with actual costs |
| eHerkenning level 3 | for submission |
| Chain authorisation | if an intermediary submits |
Reporting WBSO realisation in 5 steps
- 1 Close the records — Finalise the hours, project and any cost records for the calendar year.
- 2 Add up the hours — Total all R&D hours realised across approved projects and declarations.
- 3 Determine costs and expenditures — Only for actual costs: determine which amounts were actually realised and paid.
- 4 Compare with the decision — Compare realisation with the awarded amount and assess whether a correction is likely.
- 5 Submit the statement — Submit through RVO's eLoket using 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 the end of the calendar year | Within 3 months after date of S&O-verklaring |
| Business terminated or bankrupt | Within 1 month |
| Withholding-agent status ends | Within 1 month |
See also the full WBSO deadline calendar.
What happens if you report WBSO realisation late?
Late reporting
A late statement can result in a fine. If you also realised less R&D than awarded, a corrective S&O-verklaring will additionally follow.
Not reporting at all
If an employer does not submit the mandatory statement at all, RVO can set the realised hours and any costs and expenditures at zero. This leads to a full correction and a fine.
Also prepare for a possible RVO audit — the statement of realisation and the underlying records must correspond.
Frequently asked questions about the WBSO statement of realisation
When must I report WBSO realisation?
No later than 31 March of the year following the calendar year in which you used WBSO. For WBSO 2026, this is therefore no later than 31 March 2027.
Must I always report realisation?
Employers always must, even if a project was not carried out. Self-employed professionals only when they realised fewer than 500 R&D hours.
I have several S&O-verklaringen. Must I submit several reports?
No. You submit one statement of realisation for the entire calendar year, regardless of the number of S&O-verklaringen received.
What must I report under the fixed amount?
Only the R&D hours realised. You do not need to report costs and expenditures separately.
What must I report with actual costs and expenditures?
The R&D hours realised plus the costs and expenditures actually realised and paid.
What if I realised fewer hours?
RVO may issue a corrective S&O-verklaring with one correction amount for the declarations for that calendar year.
What if I realised more hours than awarded?
That does not generate additional WBSO. The awarded amount is a maximum.
Can I move hours between projects?
Yes, under certain conditions within the same calendar year and within already approved projects and awarded hours. Hours and euros cannot be exchanged with each other.
What if I report too late?
This can result in a fine and, where realisation is lower, also a corrective S&O-verklaring.
What happens if a project did not start?
An employer must still submit a statement. The realised hours are then zero, which leads to a correction.
Practical tip: compare awarded and realised hours per project. Structural under- or overestimates provide a good basis for a more realistic WBSO budget for the following year.
RELATED PAGES
WBSO administration → WBSO hours registration → WBSO project records → WBSO costs and expenditures → WBSO deadlines → RVO audit → Objecting → WBSO calculator →
Is your WBSO statement of realisation correct?
We check your realised hours, costs and expenditures and assess in advance whether a correction is likely — before you submit.
Have my WBSO realisation reviewed 033 – 453 08 18
SOURCES AND SUBSTANTIVE REVIEW
RVO — WBSO Guide 2026
Reviewed by Peter Klaren, WBSO specialist since 2004. Last substantively updated: 21 September 2026.