Wis. Stat. § 628.39

The extension of credit to the insured upon a premium without interest for not exceeding 60 days from the effective date of the policy, or after that time with interest at not less than the legal rate nor more than 18% per year on the unpaid balance, is permissible. The payment of premiums on policies issued under a mass marketing program on an installment basis through payroll deductions is not an extension of credit.