@ethicsgirl,
7 years.Your question has the answer.
However I did find some of fellow candidates confused on account of the undernoted discussion:
Local Requirements
“Local regulators often impose requirements on members, candidates, and their firms related to record retention that must be followed. Firms may also implement policies detailing the applicable time frame for retaining research and client communication records. Fulfilling such regulatory and firm requirements satisfies the requirements of Standard V(C). In the absence of regulatory guidance or firm policies, CFA Institute recommends maintaining records for at least seven years.”
This should mean fulfilling local requirements satisfies the requirements of Standard V(c).
“In the absence of regulatory guidance….cfa institute recommends maintaining for at least seven years”.But if 5 years is the local norm “Regulatory guidance or firm policies” are not ABSENT.
And V(C) DOES NOT talk about applying stricter norms….so 5 years may “satisfy”…..reason for the confusion.Is that the reason for your doubt,though not stated?
Read with Standard IA

rofessionalism.”Members and Candidates must understand and comply with all applicable laws, rules, and regulations (including the CFA Institute Code of Ethics and Standards of Professional Conduct) of any government, regulatory organization, licensing agency, or professional association governing their professional activities.In the event of conflict, Members and Candidates must comply with the more strict law, rule, or regulation.”
Even if Local laws are NOT ABSENT(present and less conservative),In case of conflict stricter law will prevail as per I(A).