Insights · 2026-10-12
UN R156 01 series: an RXSWIN for every approval you update
In brief
- 01
The 01 series of amendments to UN R156 was adopted by WP.29 in November 2025 and entered into force on 4 June 2026.
- 02
The SUMS must now include a process that assigns a dedicated RXSWIN for every UN Regulation X approval whose relevant software the manufacturer updates.
- 03
Registered vehicles approved to the 01 series may not receive software updates unless every approval assessed in the update process has an RXSWIN.
- 04
Approvals to the original version phase out: from 1 September 2028 for new ones, from 1 September 2030 for all, with exceptions for vehicles the changes do not affect and for extensions.
- 05
The freedom to scope RXSWINs loosely narrows. The mapping from software to approvals has to be explicit, recorded and kept true.
UN R156 has a new series of amendments, and it is about one thing: RXSWIN. Under the 01 series, in force since 4 June 2026, a manufacturer that updates software relevant to a type approval must identify that software with an RXSWIN for that specific approval. What used to be a scoping choice is now a rule.
What was adopted
The proposal for a 01 series of amendments to UN Regulation No. 156 was adopted by GRVA, the UNECE Working Party on Automated/Autonomous and Connected Vehicles, at its twenty-second session. The World Forum for Harmonization of Vehicle Regulations (WP.29) adopted it at its 197th session in November 2025, and it entered into force on 4 June 2026. The text is ECE/TRANS/WP.29/2025/142.
It changes R156 in three ways: new requirements on RXSWIN, an amended information document, and new transitional provisions.
The two new rules
An RXSWIN per approval. A new paragraph 7.1.1.3 adds a process to the SUMS requirements. The manufacturer must assign a dedicated RXSWIN for every UN Regulation X type approval to which it executes software updates of type-approval-relevant software. In plain terms: if you update software that contributes to, say, an approval for braking or for lane keeping, that approval needs its own identifier.
No updates without them. A new paragraph 7.1.4 says the manufacturer shall not execute software updates to vehicles approved to the 01 series that are already registered, unless an RXSWIN has been assigned to every UN Regulation X approval assessed during the update process. The identifier is no longer documentation that follows an update. It is a precondition for doing one.
The information document follows the same line. The approval file now asks how to read any RXSWIN, or the relevant software versions where the RXSWIN is not held on the vehicle, and how to access the auditable register of all software versions relevant to any RXSWIN.
The transitional dates
The new paragraph 13 sets out the transition:
- From entry into force, no Contracting Party applying R156 may refuse approvals to the 01 series.
- From 1 September 2028, Contracting Parties are not obliged to accept approvals to the original version first issued after that date.
- Until 1 September 2030, they must accept approvals to the original version first issued before 1 September 2028.
- From 1 September 2030, they are not obliged to accept approvals to the original version at all.
Two exceptions soften this. Approvals to the original version continue to be accepted for vehicles that are not affected by the changes in the 01 series, and extensions of existing approvals to the original version continue to be granted.
Guidance is following
In April 2026 an amended interpretation document for R156, prepared by a UNECE task force, was put forward for the June 2026 session of WP.29. It is aligned with the 01 series and cites ISO 24089:2023 as supporting reference. The interpretation document is guidance, not requirement, but it is where approval authorities and technical services look first. We described what ISO 24089 asks of an engineering organisation separately.
What it means for engineering
RXSWIN was always easy to define and hard to keep true. The 01 series removes most of the room in between. A manufacturer can no longer decide that some approvals are covered loosely by a broad identifier. Each updated approval needs its own, and the vehicle cannot be updated until they exist.
That makes three things load-bearing:
- An explicit map from software to approvals. For every software item that is updated, you need to know which Regulation X approvals it contributes to. That map has to exist before the first update, not be reconstructed during one.
- A record that holds across variants. The RXSWIN is only as good as the vehicle configuration information beneath it: the baseline, the coded values and their ODX description. Thousands of variants make this a configuration-management task, not a labelling task.
- Suppliers who can evidence their part. The RXSWIN belongs to the vehicle manufacturer, who owns the approval. Suppliers meet the rule through what their ECUs and tools can show: which software is installed, which configuration it runs, and a traceable record of what was written to which vehicle.
None of this is new engineering. It is the discipline UN R156 has asked for since 2021, with less room to postpone it.
Standards cited here last checked against the issuing bodies on .