OSS (One-Stop Shop for EU VAT)
One quarterly EU VAT return instead of a registration in every country you sell to.
What it is
The One-Stop Shop is the EU's single return for cross-border sales to consumers. Since 1 July 2021, an EU-based seller whose sales to consumers in other member states pass €10,000 a year charges each buyer the VAT rate of the buyer's country, then declares all of it once a quarter through one tax office.
Why it costs you money
Below the threshold you charge your home rate everywhere; above it, a German buyer pays 19% and a Hungarian buyer 27% on the same product. A store still charging one rate after crossing the line is underpaying VAT on every foreign order, and the shortfall comes out of margin later.
How to check it yourself
Total last year's consumer sales to other EU countries from your WooCommerce orders and compare them with €10,000. If you are over, your tax table needs a row per member state and the tax base set to the customer's shipping address, not your shop address.