Reader question: Paying wealth tax in the Netherlands after emigration to Thailand?

In the year that you sold your house and you transferred the amount of money (equity) received for this to your Dutch bank account, this must be stated on your income tax return form in box 3 for that year. If you have failed to do so and you exceed a certain amount, you will owe tax. This can certainly put you in conflict with the tax authorities.
I found this on the internet:

Taxes 2018 – box 3

Your (fictitious) income from savings and investments is taxed in box 3. We call the tax levied in box 3 capital yield tax. Your income from assets is calculated with a fixed return. The actual return you achieve is irrelevant to the tax authorities. This fixed return used to be one fixed percentage of 4%, but as of 2017 it depends on the amount of your total assets.
A fixed tax percentage of 30% is calculated on the calculated return. This means that the levy on capital for the year 2018 amounts to a percentage ranging from 0,60% to 1,61%.
Every taxpayer has an exemption in box 3: an amount on which you do not have to pay tax. This tax-free allowance is €2018 for 30.000 (€2017 in 25.000).

tax on box 3 capital from 2018 Fixed return 30% tax
Band Assets from savings and investments* Percentage 0,36% Percentage 5,38% Effective
0 First €30.000 Exemption 0,00%
1 Above exemption, from € 1 to € 70.800 67% 33% 0,60%
2 From €70.801 to €978.000 21% 79% 1,30%
3 From €978.001 0% 100% 1,61%

*The starting point is the assets per person: the value of assets minus the debts of each taxpayer on 1 January of the year for which you are filing a tax return. An exemption applies to the first € 30.000: no wealth tax has to be paid on this amount. This is shown by disk 0 in the table above. (For married couples 2x 30.000 euros is 60.000 euros in exemption.)

Apparently you emigrated to Thailand in the year after the sale. Whether you are still a taxable person is up to you to judge. Failure to provide or incomplete information to the tax authorities is punishable by law

This is what I found about post-requisition assessment.

A final tax assessment is sometimes not final after all

If you think that your tax return has been approved by the tax authorities, because you have been notified in writing by means of a final assessment, you would be surprised if they still come back to this (often after many months) and impose an additional assessment. But can the IRS do that? Surely definitive means final and not provisional?

Provisional assessment or final assessment
If a provisional assessment was the last message from the tax authorities for that tax year, it is of course logical that a final assessment is still issued. After all, the tax return had not yet been definitively approved. However, if you have received a final assessment, the rule applies that the tax authorities cannot, in principle, go back on it. But there are exceptions.
errors in the declaration
If errors have been deliberately made in the tax return, the tax authorities may reconsider without any discussion. For example, if things have been concealed or incorrect information has been given. For example, if you have not stated certain income or assets, this will of course be assessed as a deliberate error. Apart from the fact that the underpaid tax is still being claimed, the chance of a fine is very high.

But you can also make mistakes by accident, i.e. unconscious mistakes. For example, you accidentally entered income from previous employment under the heading income from current employment, as a result of which you incorrectly received an employed person's tax credit without realizing it. Who can know this now. In this example, there is clearly an unconscious error, and the tax authorities will also be able to reconsider the previous final assessment.
If the tax authorities already had all the information
If the tax authorities could easily trace this unconscious error themselves, for example because the benefits agency is a pension fund and the tax authorities could therefore sense that this concerned income from a previous employment, you could object to the assessment. The rule is that the tax authorities may not go back on a previous final assessment if they already had all the correct information at that time.

If you have accidentally made a mistake, the tax authorities may make an additional claim against a previous final assessment, if there is a new fact. In other words, information that the tax authorities did not have available at the time of processing your statement

If the tax authorities have imposed too little tax due to their own error, which an average taxpayer should reasonably have noticed, the authority can also reconsider. If you have paid more than 30% too little tax, the service has no mercy, even if you, as the average taxpayer, could not possibly know that the tax authorities have made a mistake. But what harm would it do to appeal against such a decision.
How long can the tax authorities go back on an earlier assessment
Before an additional assessment is imposed, the tax authorities first send a letter with a text and explanation.
• The tax authorities may not continue to impose additional assessments indefinitely. The service can send an additional tax assessment up to a maximum of 5 years after the end of a tax period (usually the calendar year). An additional tax assessment can therefore be imposed for 2016 until December 31, 2021.
• If it concerns an error made by the tax authorities that one wants to correct, the additional tax assessment must be imposed within 2 years after the end of the period in which the tax debt arose.
• Do you have income in or from a country other than the Netherlands? An additional tax assessment can then be imposed up to a maximum of 12 years after the end of the tax year.

Advice
If you are confronted with a correction to a final assessment, check whether there has been an unconscious error and whether the tax authorities should logically have seen this error earlier, based on the information it had at the time of filing the tax return. If so, appeal. No you have and yes you can get.
For all details, consult belastingdienst.nl and search for “additional assessment”.