# Why a Retained Tax Record Should Remain Independently Verifiable

A recipient should be able to test whether the retained final bytes remain intact without needing the originating software to render or compare them.

## Bounded UD model

Existing tax systems continue calculation, validation, transmission and acceptance. UDR records change; UDS preserves an exact final state; an amendment creates new lineage.

## Claims boundary

Integrity does not prove filing acceptance, tax correctness, legal sufficiency, compliance, admissibility or freedom from penalties.

## Primary context

- https://www.irs.gov/pub/irs-pdf/p4164.pdf
- https://www.gov.uk/guidance/use-making-tax-digital-for-income-tax/create-digital-records
- https://developer.service.hmrc.gov.uk/guides/vat-mtd-end-to-end-service-guide/

- Demo: https://universaldocument.org/tax/demo
- Pilot: https://universaldocument.org/tax/pilot