The normal date before which you should have filed your tax return of the previous year is April 1. What if you have not done so? And what if the tax office is not chasing you to do so?
In that case you did not have a filing obligation or your tax advisor has put you in his extension rule and then the tax office is going to chase you a year later if you have not done the tax return by then while having a filing obligation.
But the focus is now on the persons that do not have a filing obligation. Who are that? That are the employees with one employer only that have never indicated to have more world wide assets than the threshold amount.
What if you did have some deduction costs such as tuition fee? Or you arrived in the Netherlands during the year, hence you can have a tax refund. Also if you left the Netherlands during the year. Then you can still file the tax return and claim back the refund.
What if you know it is not a refund that applies to you, but you are due tax. Tax due to the fact that you did have in the world more assets than the threshold amount? Or you did have income earned abroad while being a tax resident in the Netherlands.
In both cases you have still five years to go back to file the income tax returns (2009-2013). For the persons that can claim back the five period ends there. For the persons that should have filed more years, than the five years we can go back, those person need assistance and come clean to the tax office before July 1 next to benefit from the Amnesty provided.