A return to work letter to a current employer should state the employee's intent to resume working with the company and when the employee intends on returning. For someone returning to the workforce, the letter should explain the reason for the break and describe skills developed during the time off.
If an employee intends to return to the same position he held at the company before his leave, that intent should be included in his letter. Any medical restrictions that may be attached to the employee's return to work should be stated in the letter, and the employee should attach a doctor's note explaining those restrictions. Some employers have regulations in place regarding an employee returning to work after approved leave, so the employee may need to check with his employer's human resource department before drafting and submitting his intent to resume working letter.
For a person returning to the workforce after time off, an intent to resume working letter should clearly outline the reasons why the employee took time off, so that potential employers understand the gap in employment time on a resume. If any transferable skills were learned during the time off, those skills should be outlined in the return to work letter.