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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 421 — Estimated Time of Arrival and Car Scheduling

The 421 transmits the estimated time of arrival (ETA) and planned schedule of a railcar between a railroad and a shipper, consignee or terminal.

Purpose

The 421 documents the planned trajectory of a car with ETAs at intermediate stages: interchange, yard, customer siding. It carries the car number, sequence of expected events, expected durations, constraints (windows, holds).

It feeds customer planning tools (when to staff the unloading dock) and on-time arrival KPI tools. Acknowledged by 997. Complementary to 214 (Shipment Status) which carries realized events; the 421 carries the forecast.

Envelope structure

The 421 travels within the three X12 envelope levels (ISA/IEA, GS/GE with functional group BA, and ST/SE). Didactic example in release 004010:

x12 example-421.x12 
ISA*00*          *00*          *ZZ*RAILROAD      *ZZ*CHEMSHIPPER   *260515*1030*U*00401*000000421*0*P*>~
GS*BA*RAILROAD*CHEMSHIPPER*20260515*1030*1*X*004010~
ST*421*0001~
BGN*00*ETA-2026-0099*20260515~
N7*BNSF*123456~
LX*1~
N4*FORT WORTH*TX*76101~
DTM*068*20260516~
LX*2~
N4*HOUSTON*TX*77001~
DTM*002*20260518~
SE*10*0001~
GE*1*1~
IEA*1*000000421~

Common segments

  • Header — ST, BGN.
  • Car — N7 (initials + number).
  • Planned legs — LX loop: N4 (location), DTM*068 (expected departure), DTM*002 (expected arrival).
  • Summary — SE.

Common pitfalls

  • Time zone: DTM must carry the time zone; a 14:00 ETA without TZ between Chicago and Houston introduces 1h of error — use an explicit qualifier or UTC.
  • Confidence interval: a "best estimate" 421 without AMT or MSG of confidence is taken seriously; a bad-order car or active trackwork must explicitly degrade confidence.
  • Refresh cadence: a 421 must be refreshed on every major event (interchange, hold); otherwise the ETA freezes and misleads customers.

Documentation

The code 421 and the name Estimated Time of Arrival and Car Scheduling 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.