When does an annuity begin?
Under FERS, the commencing date of an annuity for an employee who retires anywhere between the first of the month and the last day of that month is the first day of the following month. For example, the annuity of FERS employees who retire on any date in June would begin on July 1, with the first annuity payment being due on August 1.

Survivors, disability retirees, or those who take a discontinued service retirement based on involuntary separation have their annuities commence on the day after separation, death, or last day of pay, as appropriate.