The actual filing mechanics — which agency, which form, which deadline — for the most common disputes.
The Consumer Financial Protection Bureau (CFPB) handles banks, lenders, credit reporting, and debt collectors specifically. The FTC handles broader consumer fraud, deceptive advertising, and scams. When in doubt, file with both — there's no penalty for filing in the wrong place.
Send disputes by certified mail with return receipt, or at minimum keep dated screenshots of any online dispute submission. In an FCRA or FDCPA claim, proof of when you disputed and what the response was is what actually determines whether you win.