From the Patreon FAQ:
Value Added Tax (VAT) is a tax assessed on the value added to goods and services — including digital. It’s charged as a percentage of a price (e.g. $1.00 pledge with 23% VAT will have a final cost of $1.23).
On Patreon, we cover the collecting and remittance of VAT charged to patrons. We’ve made these guides to help creators and patrons through how VAT applies to them:
For patrons, we list the amount of VAT added to your membership payments on your Billing History page, where you can also download a VAT-compliant invoice beginning December 1, 2021.