You need to add an invoice address during the booking process in step 4 to actually be able to make a booking.
To add a new invoice address:
1. Click on "Add an address"
2. Add your new invoice address and details. Make sure the emailaddress is the address of the person who is responsible for your finances and invoices. As a default we prefill the emailaddress you use to register.
3. Click on Add your address button
4. Double check your address
In your account
You can also add a (new) invoiceaddress through your account. First make sure you are logged in and go to your account.
Click on "My addresses" in the left menu or on the orange button "My Addresses". If you have not added an address yet you can add a new one by filling in the form.
If you want to add a new invoice address, either edit your existing invoice address or add a new one through the form. You can then select the address you want to select as default.