If you forget to declare your VAT, the Danish Tax Agency will automatically assess the VAT amount you have to pay. You will also be charged a fee and interest, if any.
Learn more on how to declare VAT on the Danish Tax Agency's website.
When you have registered your company for VAT, you must declare VAT for each VAT period. Information about the VAT period is given in connection with registration.
You will need this:
You will need your MitID or passcode for E-tax for business. You can order it here
Documentation in the form of VAT vouchers