The letter of acknowledgement, as the name suggests, is an acknowledgement that the firm has received the invitation to tender and asks that the tenderer informs you whether it intends to make a submission.
If the tender documentation has been provided electronically, you may ask that the letter of acknowledgement is returned electronically using the form of words provided. If an electronic tendering system is being used the system will usually have the functionality for tenderers to opt in or out of the tender opportunity.
An example of a letter of acknowledgement is provided.