Assign a default Payment Method for each supplier to Supplier Site.

Set up payment bank accounts with the appropriate Danish Payment formats defined as payment documents.

Check that your Home Country is set to Denmark. You can define the Home Country in the Define Financials Options window
(Setup > Options > Financials). In the VAT Registration Information region, change the Member State field to Denmark. None of the flexfields will display the correct prompts unless the Home Country is set to the correct country.

Set up the company's taxpayer ID in Reporting Entities.