Wis. Stat. § 344.34
When an insurer has certified a motor vehicle liability policy under s. 344.31 or a bond under s. 344.36 , the insurance so certified shall not be canceled or terminated until at least 10 days after a notice of cancellation or termination of the insurance so certified has been filed in the office of the secretary. No insurance so certified may be canceled or terminated by the insurer prior to the expiration of 90 days from the effective date of the certification on the grounds of failure to pay a premium when due. Such a certified policy or bond subsequently procured shall, on the effective date of its certification, terminate the insurance previously certified. Any certification or recertification filed by the same insurer following cancellation shall be accompanied by a fee of $3 payable by the insurer.
Wis. Stat. § 344.34
The failure of an insurer to comply with the notice requirement under this section precludes the insurer from asserting that a previously certified policy had lapsed. Lang v. Kurtz, 100 Wis. 2d 40, 301 N.W.2d 262 (Ct. App. 1980). The 10-day notice of cancellation requirement only applied to liability coverage of a policy acquired to satisfy proof of financial responsibility. Uninsured motorist coverage cancellation took effect immediately. Nutter v. Milwaukee Insurance Co. 167 Wis. 2d 449, 481 N.W.2d 701 (Ct. App. 1992). The 10-day notice requirement in this section results in a period of time in which the insurer owes coverage to the public despite the fact that its policy with its insured was not contractually in force. However, s. 344.33(7) allows an insurer to recover from its insured any claims it paid that it would not have been obligated to pay but for the Financial Responsibility law. When the insured's policy lapsed 3 days before an accident, but the insurer did not send a notice of cancellation to the state under this section until after the accident, the insurer had a responsibility to cover 3rd-party losses and was entitled to seek reimbursement from the insured under s. 344.33(7). Acuity v. Albert, 2012 WI App 87, 343 Wis. 2d 594, 819 N.W.2d 340, 12-0382.