Like these termination letter samples, your own letter will need to be extremely tactful and diplomatic; aim to make a clean and honest break. Your message should include every detail the employee will require in order to move forward, but it should also omit bits that may put the company in an awkward position later.
Core information: In your first few sentences, announce the termination, state the name of the person and his or her position, the name of the company, as well as the dates of the letter and official termination.
Warnings: List all the warnings that have occurred, both written and verbal.
Reasoning: Provide a reason for the termination, whether the fault does or does not lie with the employee.
Company property: State the items that the employee will be expected to turn over to the company before leaving, including computers, keys, vehicles, or supplies.
Vacation pay, severance, and benefits: Either list and explain the remaining loose ends regarding payment and benefits, or clearly explain how the employee will receive this information.
Keep your details clear and accurate: The information in your letter absolutely must be correct, with nothing omitted, no excess, and no room for misinterpretation.