Explain sanctions screening.

Sanctions screening checks people and activity against sanctions lists (EU, UN, US OFAC/SDN, UK OFSI, others) to prevent dealing with prohibited parties or jurisdictions. You screen at multiple points: customers and beneficial owners at onboarding and on an ongoing basis (and re-screen when lists update), and transactions in real time (payments, trade finance), plus counterparties, vendors, and sometimes employees. Key complexities: name-matching generates false positives (fuzzy matching, common names) needing disposition; the OFAC 50% rule means entities owned ≥50% by sanctioned persons are themselves blocked even if unlisted, so you must trace ownership; and secondary sanctions mean US sanctions can reach non-US firms (e.g., USD-clearing or dealings with SDNs). Hits must be investigated, escalated, and frozen/reported as required, never simply cleared for speed. Breaches are strict-liability with severe penalties, so screening is a core, continuously-tuned control.