APPLICATION CALENDAR · UPDATED 19 SEPTEMBER 2026

WBSO deadlines 2026: when do you have to apply?

WBSO must always be applied for in advance. For employers, the rule is normally the last day of the month before the desired start month. The application window for a start in the final months of 2026 (30 September 2026) has closed. The next deadline is 20 December 2026: employers wishing to claim WBSO from 1 January 2027 must submit their application by that date. For later start months in 2027, applications must generally be submitted before the start of the month concerned. Self-employed professionals have different application moments.

BY PETER KLAREN · SOURCE: RVO WBSO GUIDE 2026

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WBSO deadlines 2026 and 2027 at a glance

The right deadline depends on your business form and desired start date. Employers always start on the first day of a month; for self-employed professionals the period starts on the day of submission.

For the substantive application steps see WBSO application and for the annual parameters WBSO 2026.

When does an employer have to apply for WBSO?

For employers and other R&D withholding parties the main rule is: submit the application no later than on the last day of the month before the desired start month.

Do you for example want to use WBSO from 1 July? Then the application must be submitted by 30 June at the latest. The application period starts on the first day of the following month and automatically runs until 31 December.

An application period must last at least three months. That is why 30 September is the last regular submission date within the calendar year. For a start on 1 January the exceptional deadline of 20 December applies.

WBSO deadline for self-employed professionals

For self-employed professionals the application period works differently. The WBSO period starts on the day you submit the application and runs until 31 December.

A minimum application period of three months also applies to self-employed professionals. As a result, 30 September 2026 is the last date on which you can still apply for WBSO for 2026. Do you want to use the scheme from the beginning of 2027? Then submit an application no later than 1 January 2027.

For the final R&D deduction, a minimum of 500 R&D hours and the fiscal hours criterion of 1,225 hours additionally apply. Check the other WBSO requirements.

Deadline near? Consider submitting an informal WBSO application

Unable to complete the full technical WBSO application before the deadline? RVO offers the possibility to first submit an informal application and supplement it later. This can prevent future R&D activities from falling outside the application period.

Note: if you ultimately decide not to proceed with the application, withdraw the informal application. Otherwise, for withholding parties it counts towards the maximum of four applications per calendar year.

How often may you apply for WBSO?

Withholding parties can submit a maximum of four WBSO applications per calendar year. For self-employed professionals there is no maximum number of applications. Read more on the page for self-employed professionals.

Do you expect new projects or more R&D hours or costs later in the year? Then an additional WBSO application may be necessary. Describe new technical activities in advance and align the planning with the remaining application moments. “Submit earlier and expand unlimitedly later” is therefore not a correct rule of thumb.

After submission, RVO may ask for clarification. See what you can expect with a WBSO information notice.

Applying for WBSO for 2027

Do you as an employer want to use WBSO from 1 January 2027? Then submit your application no later than 20 December 2026. For self-employed professionals the application period starts on the day of submission; those who want to use the scheme from 1 January 2027 must submit an application no later than 1 January 2027.

The announced percentages and amounts for 2027 are not yet final. The application planning for a 1 January start is already relevant. View WBSO 2027 →

Reporting WBSO 2026 actuals: by 31 March 2027

Did your company use WBSO in 2026? Then 31 March 2027 applies as an important next deadline.

Withholding parties report the realised R&D hours and, if applicable, the actual costs and expenditures. Self-employed professionals file an actuals report when they have realised fewer than 500 R&D hours.

Everything about reporting WBSO actuals → Keep a consistent WBSO records throughout the year.

Frequently asked questions about WBSO deadlines

SOURCES AND SUBSTANTIVE REVIEW

RVO — WBSO Guide 2026

Reviewed by Peter Klaren, WBSO specialist since 2004. Last substantively updated: 21 September 2026.