Tax forms on Upwork (W-9, W-8BEN) are the United States tax certifications that Upwork, as a US company paying freelancers worldwide, asks every freelancer and agency to complete before it will release earnings.
Upwork Inc. is a US company, so US tax law governs what it must collect from the people it pays. A freelancer or agency owner in the United States completes a Form W-9, giving their taxpayer identification number; Upwork uses it to report what it paid them to the Internal Revenue Service on a Form 1099-K when the IRS thresholds are met, and those thresholds change from year to year. Everyone outside the United States completes a W-8BEN as an individual or a W-8BEN-E as a business, which certifies that they are not a US taxpayer and so are not subject to US withholding on their Upwork earnings. Upwork's Help Center describes both forms and states that an account without the right form on file cannot withdraw funds.
The forms are not tax payment. Upwork does not withhold income tax on behalf of a freelancer's home country, and an independent contractor remains responsible for declaring Upwork income locally. What Upwork does collect, in a growing list of countries, is value-added or goods-and-services tax on its own fees, charged unless the freelancer supplies a registered tax number, and it reports income to tax authorities in jurisdictions that require platforms to do so.
For an agency the form belongs to the legal entity behind the agency financial account, not to each member, since the agency, not the member, is the party Upwork pays.
How Upwork Insights uses it
This term describes Upwork's own rules or product rather than a figure the index measures; the pages that do carry live figures are the stats and rate pages.