Under FINRA rules, which of the following activities by a registered representative requires written notification to her firm?

Driving part time for a transportation network company on weekends is the correct choice that requires written notification to the registered representative’s firm under FINRA rules. This is because engaging in outside business activities—especially those that involve compensation—must be reported to the firm to avoid conflicts of interest or any potential misuse of inside information. The firm needs to ensure that the representative's outside activities do not interfere with their obligations to the firm or compromise the interests of their clients.

On the other hand, volunteering at a local charity does not typically require notification as it is generally considered a non-compensated activity. Investing in stocks for personal gain falls under personal investment activity, which usually doesn’t need to be reported unless the individual is also involved in managing those securities on behalf of others or it involves account activity that could conflict with the firm’s interest. Attending industry seminars, where representatives are likely to learn and network without engaging in compensated work, does not require notification either, as it pertains to professional development within the guidelines set by FINRA.