Explanation
REPORTING OF SUSPICIOUS TRANSACTIONS [https://www.fatf-
gafi.org/media/fatf/documents/recommendations/pdfs/FATF%20Recommendations%202012.pdf] If a financial institution suspects or has reasonable grounds to suspect that funds are the proceeds of a criminal activity, or are related to terrorist financing, it should be required, by law, to report promptly its suspicions to the financial intelligence unit (FIU). According to the Financial Action Task Force's (FATF) Recommendation 20, a suspicious transaction report (STR) or a suspicious activity report (SAR) is filed by a financial institution or, by a concerned citizen, to the local Financial Intelligence Unit if they have reasonable grounds to believe that a transaction is related to criminal activity.
[https://aml-cft.net/library/suspicious-transaction-report-str-suspicious-activity-report-sar/]

According to the FATF Recommendations, financial institutions should maintain all necessary records on transactions and customers for at least five years, and make them available to competent authorities upon appropriate authority1. This includes records and documents related to suspicious transactions that have been reported to the financial intelligence unit (FIU) or other designated authorities. Providing the supporting documentation to competent authorities upon request is essential for the investigation and prosecution of money laundering and terrorist financing offences, as well as for the identification and tracing of criminal assets2.
Hinting to the customer that she should come in and explain her behavior is not a correct answer, as it may tip off the customer about the suspicion and compromise the effectiveness of the reporting system. Financial institutions should not disclose to the customer or to third parties that a suspicious transaction report (STR) or related information is being reported to the FIU3.
Maintaining adequate written documentation of all individuals and transactions reported is not a sufficient answer, as it does not imply cooperation with competent authorities. Financial institutions should not only keep records, but also provide them to the authorities when requested.
Submitting information upon receiving a legal request from parties involved in a civil lawsuit is not a relevant answer, as it does not relate to the cooperation with competent authorities for AML/CFT purposes. Civil lawsuits are not part of the AML/CFT framework, and financial institutions should not disclose confidential information to private parties without proper legal grounds.
References:
FATF Recommendation 11: Record-keeping 1
FATF Recommendation 31: Powers of law enforcement and investigative authorities 2 FATF Recommendation 21: Tipping-off and confidentiality 3