It is possible to have a VAT-number but no membership to the Chamber of Commerce. This come in handy if, for example, you rent out a vacation home so you can deduct the VAT on costs spent on maintenance of said vacation home. In this case a membership to the Chamber of Commerce is not necessary.
Don't panic! If this describes your situation, you can just enter your VAT-number in your E-Flux account. Based on this information we will compose your reimbursement invoice wíth VAT. The billing invoice will always contain VAT, regardless of whether or not you're VAT liable. E-Flux' billing invoice will always contain VAT, since E-Flux is an operating business.