Part one — the technical dossier
Built in IUCLID format, the technical dossier is where substance identity, properties and study data live. Its sections map to the IUCLID structure.
| Section | Content | Where dossiers fail |
|---|---|---|
| 1. Identification | Substance identity, composition, analytical data, registrant and role | The single most common cause of rejection. Composition must be supported by real spectra and chromatograms, not a specification sheet. |
| 2. Classification | GB CLP classification and labelling | Inconsistency between the dossier classification and the SDS actually in circulation. |
| 3. Manufacture and use | Identified uses, uses advised against, tonnage | Uses drafted too narrowly, so a customer's real application falls outside the registration. |
| 4–7. Study data | Physicochemical, environmental fate, ecotoxicology, toxicology | Robust study summaries too thin to be independently assessed. |
| 11–13. Guidance | Safe use guidance, exposure scenarios, assessment reports | Exposure scenarios that do not match how the substance is genuinely handled downstream. |
| 14. Testing proposals | Proposals for higher-tier vertebrate studies | Testing started before the proposal was decided — the data is then submitted unlawfully. |
Substance identity is the foundation
Everything else in the dossier describes this substance. If identity is wrong or under-evidenced, the studies attached to it prove nothing, read-across to it cannot be justified, and the registration can be invalidated years later.
For a well-defined mono-constituent substance this is straightforward. For UVCB substances — those of unknown or variable composition, complex reaction products or biological materials — it is the hardest part of the entire project, and the part most often underestimated.
Robust study summaries are not abstracts
A robust study summary must contain enough detail for an assessor to judge the reliability of a study without reading the full report: method and guideline, deviations, test material identity, doses, results, and a reliability rating with reasoning. Summaries copied from a supplier's SDS or a public database entry do not meet the standard, and HSE will say so.
Part two — the chemical safety report
Required at ten tonnes a year or more. The CSR documents the chemical safety assessment: what the substance does, who is exposed, at what level, and whether the risk is controlled.
Hazard assessment
Human health, physicochemical and environmental hazard, leading to DNELs and PNECs — the threshold values against which exposure is judged.
PBT and vPvB assessment
Whether the substance is persistent, bioaccumulative and toxic, or very persistent and very bioaccumulative.
Exposure assessment
Exposure scenarios for each identified use across the lifecycle: manufacture, formulation, industrial and professional use, consumer use, service life and waste.
Risk characterisation
Estimated exposure compared with the threshold values. Ratios must be below one for every scenario, or the use cannot be supported.
Where the substance is classified as hazardous or assessed as PBT/vPvB, the exposure scenarios must be annexed to the safety data sheet and passed down the supply chain — turning the CSR into a document your customers read and rely on.
Submission and what happens next
Submit
Through the HSE Comply with UK REACH service, with the IUCLID file and the fee.
Completeness check
A technical and financial completeness check. Failures come back with a deadline to correct.
Registration number
Issued on successful completion. Market access follows from this point.
Evaluation
HSE may select the dossier for compliance check or the substance for evaluation, at any time afterwards.
A registration number is not the end of the obligation
The dossier must be kept current: new hazard information, changes in tonnage band, new identified uses, changes in composition, and responses to HSE decisions all require an update. Ongoing duties →
How we build them
- Substance identity established first, with analytical work commissioned where the existing characterisation will not hold.
- A written data gap analysis against the annexes for your band, before any spend is committed.
- Non-testing evidence developed wherever it is defensible — QSAR, read-across, weight of evidence, waivers — with the justification written to withstand a compliance check.
- Robust study summaries prepared from full study reports, not from secondary sources.
- Exposure scenarios drafted against how your customers actually use the material, gathered from them rather than assumed.
- Submission handled end to end, including completeness failures and HSE correspondence.
General description of UK REACH registration dossier structure. Requirements differ by tonnage band and substance type; UVCB and intermediate registrations follow different routes.