Hello, I am Keith, one of the experts on Just Answer, and happy to help you with your question.
Were your Danish customer registered the reverse charge system would apply where you charge VAT and reclaim in on the same trnasaction rendering an EU Sales List at intervals. In the absence of Danish VAT data from your customer you must charge VAT on your invoice. Here is an extract from Smarta:
'Reporting your exports to HMRC: You must report your EU sales and the VAT charged to HMRC using:
Your VAT return (Boxes 6 and 8)
Your EC Sales List (ESL) - you get sent this automatically after ticking Box 8 of your VAT return (find out more in Resources, below) If you sell more than
£260,000 of goods to EU countries in a year, you must also fill out the Intrastat Supplementary Declaration.'
As you will be charging VAT as normal you do not have to worry about EU Sales Lists etc. It is just a normal VAY standard rated supply.
I do hope that I have assisted you with your question.