This post is part of our occasional series on AML program fundamentals which focuses on refreshing foundational knowledge for experienced members of the AML community and providing an introduction to key topics for those new to the subject. Financial Institutions (FI) file Currency Transaction Reports (CTRs) which enable law enforcement to monitor and investigate potentially suspicious activity. CTRs act as a paper trail for cash transactions, and are filled out by bank personnel for each deposit, withdrawal, currency exchange or other payment or transfer greater than $10,000 in currency. In turn, the Financial Crimes Enforcement Network (FinCEN), a branch of the U.S. Treasury, reviews and correlates the customer and transaction data, and maintains a database of all filings. Nearly 50 years ago, CTRs came into existence under the Bank Secrecy Act (BSA), which established program, recordkeeping, and reporting requirements for FIs. Since then, the CTR form has been modernized several times to streamline and simplify submission requirements, and an electronic filing requirement for all CTRs was instituted. Beginning in the 1990s, FinCEN sought to reduce unnecessary regulatory burdens on filers and eliminate items which are of limited value to law enforcement. To reduce information collection, criteria were established to exempt transactions by certain entities from CTR filings.