If the insurer unreasonably delays or unreasonably refuses to pay compensation, attorney fees or costs, or unreasonably delays acceptance or denial of a claim, a penalty, payable to the worker, of up to 25 percent of the amounts then due, may be assessed. When there are no “amounts then due” upon which to assess a penalty, no penalty will be issued. A “violation” is:

The late payment or the nonpayment of any single payment due. A continuous underpayment. In the case of a continuous underpayment, all prior underpayments will be considered as one violation, regardless of when the first underpayment occurred. Or a late issuance of an acceptance or denial notice.