As of January 1, 2014, the interest for unpaid personal income tax will be at least 4% and at least 8% for corporate income tax.

To avoid (substantial) amounts of tax interest being due, we advise to file a request for an (additional) preliminary assessment within 4 months after the end of the tax year/bookyear, or to file your 2013 tax return before April 1, 2014.

Also if you expect a refund it could be recommendable to request for a preliminary refund.