Some clients require the two-letter country code in front of their VAT number, i.e. DE xxxxxxxxx. Entering this in client details throws an error for EC sales list. How?

When I run the report and export it to Excel ready to upload to HMRC, if I've added in the country code to the client's details so it shows on the client's invoice, the VAT number is report as invalid, as the digits and country code need to be separate. This is what I get:

Country code          VAT No.

DE                             DE897420583

So then I have to go through and manually remove the extra DE to be able to submit the return.

This is what I need:

Country code          VAT No.

DE                             [removed]

But if I don't add the DE to the VAT number in the client's details, then it doesn't show on the client's invoice.