One of the highest regarded things that enable an employee to leave employment without burning any bridges and leaving a final and positively lasting impression to the company is a resignation letter. The letter should be submitted in a timely manner because it spells out the time of notice and the date the employee finally leaves the company. It should be formal and professionally formatted too. It should be concise without much detail. However, some letters do call for more information, in which case, one ought to decide how much information should be given in the letter.
To write a good resignation letter, one ought to have served long productive years in the company. Further, complete all outstanding projects that one has been working on and show commitment in doing so.
It is always prudent to mention the experience and enjoyment one received while working for that company, more so if the tenure has been long. Be careful not to air any long-held grudges and grievances.
Finally, show in the letter that under the right circumstances and at the opportune chance of a position falling vacant, one can return to the organization. Leaving a company in good terms earns the employee good references plus good networking possibilities in future. Always keep a copy of the letter.