Resources and Forms. RESOURCES. In the opening paragraph of the letter enter the job position that is being offered, then enter the name of the company that is the Employer.You complete a Certificate of Service or Proof of Service form that describes how and when you served the papers. In the formal offer letter, provide comprehensive details about the position, compensation, benefits, and other pertinent terms. Step 2 - Complete the Document. Fill out all relevant fields in Form 1008ES, take a break, and then review.