Downstream users may choose to prepare a chemical safety report if their use is unsupported (outside the conditions described in the exposure scenario provided by the supplier). This includes situations where their use is advised against by the supplier, or if they want to keep the information on their use confidential. The chemical safety assessment is documented in a chemical safety report, which should be kept up to date and available.

A downstream user chemical safety assessment only needs to address the uses that are not covered in the received exposure scenarios. There is no requirement to undertake a hazard assessment if the downstream user considers the hazard assessment reported in the safety data sheet to be appropriate.

The chemical safety assessment itself is documented in a downstream user chemical safety report, which must be completed within twelve months of receipt of the safety data sheet for a registered substance, but does not have to be submitted to ECHA. The downstream user should report to ECHA that they intend preparing a chemical safety report within six months. This is called a downstream user report.

There are a number of cases where downstream users do not need to carry out a chemical safety assessment. These are when:

• A safety data sheet is not required for the substance. For example, because it is not classified as hazardous.
• A chemical safety report is not required for the substance. For example, because the registered tonnage is below 10 tonnes.
• The substance is present in a mixture in a concentration below that for which a chemical safety report is required  (this is typically at classification limits and is set out in Article 14 (2) of REACH). 
• Downstream users use the substance in a total quantity of less than one tonne per year.
• Downstream users use the substance for product and process oriented research and development (PPORD).

If either of the last two points apply, the downstream user must report this exemption to ECHA. The situations where DU CSR exemptions apply and where reporting is required are summarised in the table below.