DUIN stands for Downstream User Import Notification, which is a requirement under UK REACH for downstream users that import chemical substances into the UK from the EU/EEA or from other countries. 

 

Under UK-REACH, downstream users must register their use of specific substances and notify the HSE of their use cases. Before downstream users can use new substances, they must provide the HSE with a notification about their intended use of the substance, which is known as the DUIN notification. 

 

The DUIN notification provides the HSE with information on how the substance will be used, as well as the downstream user's contact details. It also helps downstream users understand their obligations under UK REACH and how they can use the substance legally and safely. 

 

The DUIN requirement applies to downstream users that import substances above one tonne per year from countries outside the UK or the EU/EEA if those substances are not registered by a company within the EU/EEA.  

 

Therefore, if a company is a downstream user and imports a chemical substance from outside the UK or the EU/EEA, it must provide a DUIN notification to the HSE before it can start using that substance in the UK market.