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Spotlight PEPPOL BIS Billing 3.0 The EU e-invoicing mandate is here — France Sept 2026, Belgium Jan 2026, Germany 2025.

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X12 149 — Notice of Tax Adjustment or Assessment

The 149 documents a tax adjustment or supplemental assessment issued by a tax authority to a taxpayer or its fiduciary.

Purpose

The 149 is used by the IRS, state revenue departments, and local authorities to formally notify an adjustment or supplemental assessment after a return examination. It carries the tax type (income, sales, payroll, excise), the tax period, the adjusted amount, penalties, interest, and a structured reason.

It is part of the electronic tax case file and complements the 826 (Tax Information Exchange) between agencies. Acknowledged by 997; the business response is a 151 (Tax Return Data Acknowledgment) or a return 826 when the taxpayer disputes.

Envelope structure

The 149 travels within the three X12 envelope levels (ISA/IEA, GS/GE with functional group TN, and ST/SE). Didactic example in release 004010:

x12 example-149.x12 
ISA*00*          *00*          *ZZ*USIRS         *ZZ*ACMECORP       *260514*1400*U*00401*000000149*0*P*>~
GS*TN*USIRS*ACMECORP*20260514*1400*1*X*004010~
ST*149*0001~
BGN*00*TN-2026-0042*20260514~
N1*PR*INTERNAL REVENUE SERVICE*24*EIN-IRS~
N1*TP*ACME CORPORATION*24*EIN-98-7654321~
REF*ZZ*RETURN-1120-2024~
DTM*RT*20240101~
DTM*RT*20241231~
LX*1~
AMT*ZZ*125000.00~
AMT*N9*8500.00~
AMT*PE*3120.00~
MSG*DEPRECIATION RECAPTURE ADJUSTMENT~
SE*12*0001~
GE*1*1~
IEA*1*000000149~

Common segments

  • Header — ST, BGN, DTM*RT (tax period).
  • Parties — N1*PR (Taxing Authority), N1*TP (Taxpayer).
  • Reference — REF*ZZ (target form or return, e.g., 1120, 1040, 941).
  • Adjustment — AMT*ZZ (adjusted amount), AMT*N9 (interest), AMT*PE (penalty), MSG (reason).
  • Summary — SE.

Common pitfalls

  • Period vs assessment: DTM*RT is the period under examination, not the 149 issue date. Confusing both backdates the liability.
  • Compounding interest: US interest compounds daily (IRC §6621); the 149 must carry interest to issue date, not to an arbitrary date — otherwise the taxpayer disputes correctly.
  • Dispute window: a 149 is not final until the appeal window has lapsed (90 federal days for a Notice of Deficiency); a system that marks the liability as due immediately violates due process.

Documentation

The code 149 and the name Notice of Tax Adjustment or Assessment are public and listed on x12.org/products/transaction-sets. The complete structure of loops, qualifiers and code lists is distributed by DISA via the proprietary Implementation Guides (TR3). ediverse.io covers only public concepts, the envelope and didactic examples.