Holiday allowance lower than expected?

I've been working in a company for 9 months and this month I've got my holiday allowance. Since I started in September, I'd expect my holiday allowance to be calculated this way:

(gross salary) x 0,96 x 9 : 12 x (taxes factor)

However, since I don't know how to calculate the taxes, I don't know the exact amount. Let's say that every month I got N Euros neat. Assuming that I pay the same percentage of taxes on the holiday allowance (which isn't true, but it can be an approximation), then this month I'd expect to get a holiday allowance equal to 72% of my neat monthly salary. This is of course, an approximative amount. But this month I have got a holiday allowance equal to 49% of my salary, which is lower than expected. The calculated amount in an approximation, but I didn't expect a difference of 23%, this is too much.

So the question is: should I regard this as an error and ask for clarifications with my HR manager, of maybe there is some extra tax that I am not taking into account? Maybe it's normal that taxes on holiday allowances are way higher than taxes on the monthly salary?

• This is the kind of thing you can always ask of your HR or payroll office, but were there specific promises about your holiday pay that led you to expect a specific amount? Commented May 24, 2019 at 19:22
• "I'd expect my holiday allowance to be calculated this way" - why do you expect this? Is this what they told you? What does your contract say about this? Commented May 24, 2019 at 19:24
• It's unclear to me if any of us will be able to answer your question since none of us really know what you were expecting or what those expectations were based on. This sounds like a perfect question for you to ask your HR or payroll staff at your employer. Explain that you're interested in knowing how the allowance was calculated, and then compare their explanation to your expectation. Commented May 24, 2019 at 19:41
• HR does make mistakes, so it's worth checking, but do not assume it's an error. Just ask HR how holiday pay is calculated. Commented May 24, 2019 at 19:41
• The most likely explanation, IMO, is that the allowance is based on the number of months worked during the budgetary year the allowance is calculated on, and that year ended a couple months ago. So your 9 months worked so far might be 7 in the previous year and 2 toward next year's vacation allowance. Combine that with using the marginal tax rate instead of the average as @SambalMinion explained. Commented May 27, 2019 at 0:11

The gross allowance is calculated from your gross salary per the formula you described, but your assumption on the tax percentage is incorrect. Your tax percentage is not constant.

You say that you pay 28% tax on your monthly wage. The lowest income tax tariff (1) in the Netherlands in 2019 is 36.65%. But you get an 'algemene heffingskorting' and do not need to pay your first EU 2500 of income tax (for the year). Some things are taxed wholly differently - i.e. a travel cost allowance. Hence, your average percentage over your monthly wage is always lower than the percentage your pay over the next euro you earn.

Your holiday allowance is 8% monthly income that you save up. Thus 8*12=96% of monthly salary, assuming your monthly salary remained constant throughout the past year. You must understand that it is income that would come on top of your monthly salary otherwise. It is thus taxed at 36.65% or 38.10% (2), with no deductions that compensate. NIBUD has a good article about this.

In my experience, the Dutch tax system is structured in such a way that you are unlikely to underpay (as a consequence of job or pay changes), but likely to overpay a little (3). And that is why you always fill out a tax return ;-)

Edit, note that the above was written hastily and is slightly inaccurate:

1. Dutch income tax uses tax brackets. I.e., as of 2022 any income over 69.4 thousand euros is taxed at 49.5%. Income below that is taxed at 37.07%.
2. Or another tariff, due to this income falling in another tax bracket.
3. Caveat: If you work a parttime job and pick up a lot of overtime, an unsophisticated accounting departement may fail to withhold the correct tax percentage, causing you to underpay. Not an issue with the tax system, simply bad accounting practices.