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New W-8BEN certification field and updated W-9 and W-8 guides

October 15th, 2026

Release Details

Release Date: October 15, 2026

Release Type

Informational – Optional action from platforms

Summary

POST /participants/customers/new and PATCH /participants/customers/{participant_code} accept a new field, is_exempt_foreign_person. Set it to true when a non-U.S. individual certifies that they are not a U.S. person and are the beneficial owner of the income. It is the W-8BEN counterpart of is_not_subject_backup_withholding. Send one of the two fields, never both.

The W-9 and W-8 implementation guides are updated:

  • The products and services that you use at zerohash set what you send. Some integrations need only name, address and tax ID. Others also send one certification field.
  • zerohash no longer collects treaty claims for individuals. Treaty claims are optional.
  • For customers who onboard through the Onboarding SDK, zerohash creates the signature, the certification fields and the W-8BEN record.

Action Required

None for existing integrations. zerohash still accepts all current fields, and there is no migration deadline.

If you send the certification through the API: send is_not_subject_backup_withholding for U.S. individuals or is_exempt_foreign_person for non-U.S. individuals. Through the API, zerohash does not create the signature and certification fields yet, so keep sending them with the new field. The guides list each field. We will announce the API update here.

Endpoints Impacted

What stays the same

  • All current W-9 and W-8 fields are still accepted.
  • Entity requirements, for W-9 and W-8BEN-E.

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