Form W-8BEN

Google has to withhold US tax on money creators earn from viewers in the United States, wherever in the world the creator lives. Submitting a W-8BEN through AdSense declares you a foreign individual and lets you claim the reduced rate your country's tax treaty allows, which for many countries pulls the withholding on US-earned royalties well down.

File nothing and the default applies, which is the full statutory rate against your US earnings. Companies and partnerships use W-8BEN-E instead. The form also expires, typically at the end of the third calendar year after you sign it, so check the status in AdSense rather than assuming the one you filed years ago still stands.