Deterministic EU CBAM Embedded Emissions Accounting and Pre-Verification Schema Validation under Regulation (EU) 2023/956 and Omnibus Amendment Regulation (EU) 2025/2083

On 1 January 2026, the European Union Carbon Border Adjustment Mechanism (CBAM) transitioned from its quarterly transitional reporting phase into its definitive financial regime pursuant to Regulation (EU) 2023/956, as amended by Regulation (EU) 2025/2083 (the Omnibus I CBAM Simplification Regulation) and operationalized by Implementing Regulation (EU) 2025/2621 and Implementing Regulation (EU) 2026/1740 of 20 July 2026. Under Article 2a and Annex VII Point 1 of the amended Regulation, the legacy EUR 150 per-consignment exemption was repealed and replaced by a strict cumulative annual net-mass threshold of 50 metric tonnes across cement, iron and steel, aluminium, and fertilisers (with zero mass exemption for electricity and hydrogen). Crossing the 50-tonne boundary triggers a retroactive full-year statutory cliff requiring Authorised CBAM Declarant status (Articles 4 and 5), accredited third-party verification of actual installation-level embedded emissions (Articles 7, 8, and 18), commencement of CBAM certificate purchasing from 1 February 2027 for 2026 embedded emissions (Article 20), quarterly 50% certificate holding buffers from 2027 (Article 22(2)), and annual surrender by 30 September following the import year (Articles 6(1) and 22(1)), backed by HICP-indexed excess-emissions penalties under Article 26(1) and heightened unauthorized-importation surcharges of three to five times that penalty (EUR 300 to EUR 500 per tonne of CO2e in base terms) under Articles 26(2) and 26(2a). Conventional enterprise spreadsheet workflows suffer from IEEE-754 binary64 floating-point drift across multi-tier precursor mass balances, functional-unit mismatches (such as elemental-nitrogen vs. gross-tonne accounting in CN 2808/2814/3102/3105 fertilisers), and XML/JSON schema rejection at the EU CBAM Registry gate. This technical note formalizes a zero-egress, deterministic fixed-point (0-ULP) state-machine methodology for pre-verification CBAM embedded emissions accounting, precursor attribution, carbon-price deduction substantiation (Article 9), and RFC 8785 cryptographic workpaper attestation. Reference Implementation & Archival Availability: A deterministic zero-egress WebAssembly (WASM) reference verification engine implementing the formal invariants specified in this monograph is maintained by TITAN Capital Forensics LLC (Albuquerque, New Mexico, USA; ORCID: 0009-0005-3920-2333) at cbamsovereign.com. No source code or executable software is distributed within this technical monograph.