Do I need to check both?
What's the difference between the SDN list and the sectoral sanctions list? Do I need to check both?
Yes, check both - they're different with different restrictions. The SDN list is a blocking list - you cannot transact with listed parties at all and must freeze their assets. The sectoral sanctions list (SSI) imposes specific restrictions on certain entities in particular sectors, but doesn't completely block them. For example, you might be prohibited from providing certain financing to an SSI entity but other transactions are allowed. Russia sanctions use sectoral restrictions heavily. I learned the distinctions at this link ofacblockedfundslawyers.com when trying to understand what we could and couldn't do with Russian counterparties. Screen against both lists and understand which prohibitions apply.