Merchants shall maintain copies of records of all consumer transactions subject to the act and all advertisements, printings, displays, publications or distributions the terms of which relate to the extension of consumer credit in order to permit an investigation pursuant to s. 426.106, Stats., for a period not less than that during which a customer may bring an action with respect to such transaction or advertisement as limited by s. 425.307, Stats.
Wis. Admin. Code Department of Financial Institutions DFI-WCA 1.80