Dear [Name]:

As you are aware, your [type of commercial] insurance is arranged on an adjustment premium basis, so we are enclosing an audit report of the figures for the period through [date].

You'll notice that the figures are higher than the original estimate. This is due to you experiencing a year of greater business activity than anticipated. The additional charge applies to the difference between the original estimate and the actual figures as shown on the enclosed sheet.

Please check the figures for accuracy, and send us a check for the amount due of $____ at your earliest convenience.

It's a pleasure to serve you. We appreciate your business and the confidence you have in the [Agency].

Sincerely,