The Acknowledgement Letter should always be addressed to the person whose work/effort is being acknowledged
It should also have details of what is being acknowledged so that a person who is not totally involved in the entire transaction can also understand the content of the letter
It should be short and crisp
Since it is only a medium of acknowledging a work/effort, it needn’t necessarily be complimenting
It should be prepared in duplicate where in one copy is handed over to the recipient and the other one is signed by the recipient as proof of receipt
If it is being sent by an organization to an individual, it should always be on the letter head of the organization