API "Please enter a suitable VAT treatment"

API "Please enter a suitable VAT treatment"

Hi,
I'm setting up a test UK business account with VAT. When I try to create a customer via the API, I get the above error:

[code] => 102005
[message] => Please enter a suitable VAT treatment.

Your API docs don't mention VAT in the customer section. Could you clarify what is required here?

Regards,
Andy