You should carefully read the information that is part of your retirement
application, and complete and submit the forms. You do not need to submit a
separate letter of resignation. A completed and signed retirement application
is equivalent to a letter of resignation.
If you are eligible for a retirement benefit, you should not resign,
intending to submit a retirement application later. This is because if you die
after separating but before filing the application no life insurance, no
survivor benefit, and no survivor health insurance coverage would be available
to your survivor(s). You should, however, complete all the other required "exit
procedures."
Read more about applying for
retirement.