Are you referring to the Form W-8BEN? This is a form used to confirm you’re not a U.S. taxpayer and that Upwork is not required to withhold taxes from your earnings. For record-keeping purposes, Upwork requires a Form W-8BEN for all non-U.S. taxpayers paid on Upwork. Once you file your Form W-8BEN, the system will activate your eligibility to access funds immediately.
If in any case you are asking about the VAT for countries in the European Union, you may refer to this help article.