If you return this form to the sender, service of a summons is deemed complete on the day you sign the acknowledgment of receipt below. General Tip for Opening Forms.Complete this step only if no Response has been filed. Complete, copy and file the following forms: Mandatory Forms. Learn what an acknowledgement receipt is and how to create one for your business (with a template and two examples). All addenda shall include an acknowledgement of receipt that must be returned. The addenda must be signed and attached to the final response. If you do not receive an acknowledgement receipt, call the EHSD Contract Bid phone number at (925) 608-4969. Welcome to Contra Costa County's on-line application process! Acknowledge receipt of this Addendum in your cover letter.