What is an Acknowledgment Code (ACK)?

Acknowledgment Code, or ACK, refers to a service that is offered by mail companies to inform the sender of a letter that the recipient has received the delivery. It is usually a form signed by the receiver and then delivered to the sender. This gives proof to the sender that the letter has been received.

How Acknowledgment Codes Work

The legal regulations governing the concept of acknowledgment of receipt vary in different countries. However, in most states, the recipient must sign on a form after receiving the package. Nowadays, this procedure is being done by electronic means where the signature is made on a touch screen that captures even the date and the document number of the correspondence being sent. If the recipient rejects the shipment and refuses to sign the ACK, a record of the refusal is input. If the post office sending the package loses the ACK, the client does not have the right to compensation. However, a duplicate may be issued if the issuer requests it and it must be signed again by the recipient or contain a written statement from the postman who made the delivery. 

Sometimes, the acknowledgment can be a brief response from a recipient after receiving a communication. This type of acknowledgment is usually delivered by large companies or state agencies where a person in contact with the other party is awaiting confirmation. For example, suppose that a citizen sends a letter to the city's secretary of the environment about the improvement of the cleaning of a beach. 

After a few days, an official returns a message of acknowledgment citing that they have received the request and they are addressing the situation. In various communication protocols between computers, an ACK is a notice sent by one computer to another acknowledging that it has received the message from it. This type of ACK is mostly used in the layers or levels forming a network such as those in the open systems interconnection model. 

The messages sent between computers may also have an error-detecting code to protect the data's integrity. If the destination device of the message has the necessary tools to carry out this process, the ACK then can be a record of the state in which the message was received, i.e., whether it arrived without errors or not. When the communication protocols are of greater complexity, additional elements such as data concerning incidents in the network or the request of forwarding some frames can be part of the message.