Software updates are a quality process
UN Regulation 156 requires vehicle manufacturers to run a software update management system (SUMS). UL Solutions summarizes its goal as making sure updates are carried out “safely, functionally, and traceably” and in line with type approval (UL Solutions).
Traceability, configuration control, impact assessment and records: those are the daily work of a quality engineer. That is why quality engineers are increasingly asked to own SUMS evidence.
Timeline
According to the UK Vehicle Certification Agency (VCA), R156 has applied to new whole-vehicle type approvals of unlimited-series vehicles since July 7, 2024, with earlier application from July 2022 where post-registration updates affect type-approved characteristics. For new completed vehicles, the date is July 7, 2029 (VCA). The closest standard is ISO 24089, Road vehicles: Software update engineering.
What the SUMS must cover
UL lists the processes a SUMS needs:
- Recording the hardware and software versions for each system and function of the vehicle type.
- Identifying which software is relevant to type approval and needs an RXSWIN.
- Defining and updating the RXSWIN.
- Identifying interdependencies, affected components and compatibility impacts.
- Assessing effects on type approval, functional safety and driving safety.
- Informing vehicle owners about updates.
- Protecting the update process from a cybersecurity perspective.
- Documenting all of the above.
If an update fails or is interrupted, it must be possible to restore the previous state.
RXSWIN in one paragraph
The Regulatory Software Identification Number (RXSWIN) identifies type-approval-relevant software. The manufacturer defines it; it should be unique for each software version in each vehicle type, and it can be read from the vehicle to show homologation status (UL). SPK and Associates give the example of a steering system under UN Regulation 79 using an identifier starting with “RX79” followed by a manufacturer-specific version (SPK and Associates).
The quality engineer’s evidence trail
| Step | Quality engineer’s question | Record |
|---|---|---|
| Change request | Why is the update needed (defect, security, feature)? | Change request, CSMS trigger if security-driven |
| Configuration | Which vehicles and ECUs are affected, and what is installed now? | Configuration baseline, software and hardware versions |
| Impact | Does it affect type-approved systems? Safety? | Type-approval impact assessment, safety assessment |
| RXSWIN | Does an RXSWIN change? | RXSWIN register update |
| Compatibility | Will it work with every affected configuration? | Compatibility analysis, test reports |
| Verification | Was it tested before release? | Test plan and results |
| Release | Who approved it, and how is it protected? | Approval record, signing and integrity evidence |
| Delivery | Was the owner informed, and did it install? | Owner notification, campaign results |
| Recovery | What happens if it fails? | Rollback design and test evidence |
The most common audit question is simple: pick an update from the field and show every record above for it.
How CSMS and SUMS connect
The CSMS (R155) identifies risks and determines when updates are needed; the SUMS (R156) delivers them safely (UL). A quality engineer should be able to show the link from a security-driven change request in the CSMS to the update records in the SUMS.
Who you work with
- Software and E/E engineers: update content and compatibility.
- Homologation: type-approval impact and RXSWIN.
- Functional safety: safety impact.
- Cybersecurity team: security triggers and update protection.
- After-sales and connected services: over-the-air delivery and owner information.
Common weaknesses
- Configuration records that do not match what is in the field.
- RXSWIN register maintained by one person in a spreadsheet.
- Type-approval impact assessed informally or not recorded.
- Compatibility tested on a subset of configurations without rationale.
- Rollback designed but never tested.
Checklist
- Configuration baseline per vehicle type current
- RXSWIN register controlled
- Type-approval and safety impact assessed for every update
- Compatibility rationale documented
- Owner information and campaign results recorded
- Rollback tested
- One field update traced end to end
How AskDona helps
SUMS evidence is spread across change systems, test reports, homologation files and campaign data. AskDona reads those records against your SUMS procedure and an R156-based checklist, and shows which steps are evidenced for a given update, with page citations. Run a sample SUMS record review on one recent update. AskDona shows the evidence; your quality and homologation teams decide.
Editor’s note: The process list and RXSWIN description come from certification-body and consultancy explainers, not the regulation text; check your approval authority’s interpretation. Dates are from the UK VCA. The LinkedIn count was supplied by the client.
FAQ
What is a SUMS? A software update management system required by UN R156 to carry out updates safely and traceably.
What is RXSWIN? The Regulatory Software Identification Number, used to identify type-approval-relevant software versions.
Which standard supports R156? ISO 24089, Road vehicles: Software update engineering.
How long is a SUMS certificate valid? UL Solutions reports three years.
References
All pages opened and checked by October 23, 2026.
| Source | Type | Used for |
|---|---|---|
| UL Solutions: Software update management system (SUMS) | Certification body explainer | SUMS processes, RXSWIN, rollback, validity |
| UK VCA: Cyber security and software updating (updated May 22, 2026) | Approval authority guidance | Dates, ISO 24089 |
| SPK and Associates: R155 vs R156 (Mar 20, 2026) | Consultancy explainer | RXSWIN example |