VAT (moms in Danish) is a different kind of tax than the one you pay off your income. The two has nothing to do with each other.
VAT is a tax of 25% to the Danish State which a company collects from its customers by adding it on top of the sales price.
The company collects the VAT and passes it over to SKAT every three months (usually).
When earning more than DKK 50.000 in a period of 12 months it is required to register a business (CVR-number) and become VAT-registered. Please notice that VAT will be calculated from a period of 12 consecutive months and not from the calendar year.
More precisely, the rules dictate that you should become VAT-registered the moment you can see that you will surpass a revenue of DKK 50.000. For example, if you earn DKK 35.000 over a period of 3 months, and expect to continue on the same level, you must VAT-register yourself at that time, and must from then start charging VAT on your invoices.
If you over a periode of 12 months earn more than DKK 50.000 and have not become VAT-registered, SKAT will calculate your VAT from your total revenue. This means that if you, for example, have a revenue of DKK 70.000 over a period of 12 months, you will be charged VAT from DKK 70.000 and not just from the amount surpassing DKK 50.000.