Businesses can be registered for a VAT number with the tax authority of whichever country they are based (for example - HMRC in the UK or the IRS in the USA).
EU MOSS is the VAT European Union Mini One Stop Shop Scheme for selling digital services to customers within the EU. You can read the European Commission's guidance on the EU MOSS here.
If you have a VAT number and are based in a non-UK EU member state, you can enter it on Bookwhen here.
Bookwhen will check that the VAT number is valid and, if accepted, your subscription payment to Bookwhen is defined as B2B (business to business). This means we won't add VAT to your invoice payment.
If you do not have a valid VAT number, your subscription payment is categorised as B2C (business to customer), and Bookwhen will charge you VAT. We transfer this VAT to the EU via MOSS as part of our regular tax submissions.