Tax documentation collection is gathering and validating the forms that establish a customer's tax identity and status at the moment their account opens: W-9 for US persons, W-8 for foreign persons and entities, and CARF or CRS 2.0 self-certification for crypto-asset reporting. Taxbit collects it through an SDK embedded in your own product, then validates, monitors, and stores it, so the record is ready before the first reportable transaction happens.

A missing or incorrect document doesn't stay contained to onboarding. It becomes a wrong filing, then a correction, then a notice, and the fines land on whoever filed it. Collecting and validating documentation at account opening is what keeps that chain from starting.

CARF self-certification is the account-opening step where a customer declares their tax residency and status for reporting under the OECD's Crypto-Asset Reporting Framework and the amended Common Reporting Standard, CRS 2.0. Taxbit collects it through the same embedded flow as W-9 and W-8. Collection has been live for all new customer accounts since January 1, 2026, and Wave 1 jurisdictions file Tax Year 2026 XMLs in 2027.

Your customer is prompted for a W-9, W-8, or self-certification inside your product, not redirected to a separate site. The form arrives pre-filled from the data you already hold, including your KYC record, so they confirm what is there and certify their TIN instead of entering it again. The account then moves into a "we're reviewing your account" state while Taxbit validates it. None of it leaves your product.

Taxbit validates, monitors, and stores it, and verifies US and foreign tax IDs automatically for new and existing customers. Every account gets a status: valid, invalid, needs action, or missing. It flags issues like needs resubmission, US indicia, or a treaty country mismatch, and tracks W-8 expiration and changes in a customer's circumstances. Each record shows which document it is, W-9, W-8BEN, W-8BEN-E, W-8IMY, or self-certification, and when it was last submitted.