As an entrepreneur subject to VAT-legislation, you have to submit a VAT return. In this return you declare the VAT charged to your customers, and deduct the VAT paid to your suppliers. So make sure that you have your VAT administration in order!
The Belastingdienst will not send you an assessment, you will have to remember to pay the amount due to the tax authorities. VAT returns are filed monthly, quarterly or annually. When filing your last VAT return for the year, please bear in mind that you will need to take all corrections and settlements into account. If after filing your return you turn out not to have declared enough VAT throughout the year, you will have to submit a supplementary VAT return.
If your turnover is less than € 20.000 in any year, on the grounds of the kleineondernemersregeling (KOR - small-businesses VAT exemption scheme) you will not need to declare or pay VAT, nor can you reclaim VAT.