An insurer shall promptly pay every insurance claim. A claim shall be overdue if not paid within 30 days after the insurer has received a clean claim. If such written notice is not furnished to the insurer as to the entire claim, any partial amount supported by written notice is overdue if not paid within 30 days after such written notice is furnished to the insurer. Any part or all of the remainder of the claim that is subsequently supported by written notice is overdue if not paid within 30 days after written notice is furnished to the insurer. Any payment shall not be deemed overdue when the insurer has reasonable proof to establish that the insurer is not responsible for the payment, notwithstanding that written notice has been furnished to the insurer. All overdue payments shall bear simple interest at the rate of 7.5 percent per year.

Link to Existing Law: WI Code Chapter 628 Section 628.36

The section does not explicitly mention PBMs or health insurance companies, thus, there is risk that this could be deemed to be inapplicable in the health insurance context.