ANSWER:
Under the retirement program established by Congress for members of the military services, a member must serve or acquire at least 20 years of qualifying or creditable years of service in order to be guaranteed retirement at 20 years.

Regular Active Duty
Twenty years on active duty is the basic eligibility requirement for military retirement. Service members who reach 20 years of active service (or qualifying reserve service, as discussed below) can receive retired pay that increases each year through a cost-of-living adjustment.

-------> • After retirement, retired pay increases when a cost-of-living adjustment is granted, usually late in the year, with the increase first appearing in January paychecks.

-------> • Retirement pay is tied solely to basic pay. Bonuses and allowances are not factored in.

-------> • Retirement pay for active duty begins immediately after separation. Eligible reservists must wait until their 60th birthday to start collecting pay, even though they may accrue the required 20 creditable years of service much earlier. Reservists who have retired from service but have not reached age 60 are known as “gray-area retirees.”

National Guard and Reserve servicemembers who complete a minimum of 20 "qualifying" years of service (creditable retirement years) become eligible for retired pay at age 60.

Note: A law passed in early 2008 allows Reserve and Guard members with 20 or more years to begin drawing retirement benefits before age 60 if they deploy for war or national emergency. For every 90 consecutive days spent mobilized, members of the Guard and reserve will see their start date for annuities reduced by three months. But this law only applies for deployment time served after Jan. 28, 2008.

A qualifying year, under this system, is a year in which the servicemember earns at least 50 retirement points during their retirement year. Inactive point credit is earned for inactive duty training, Reserve membership, equivalent instruction, and correspondence courses.

By law, members may receive credit for up to 60 inactive points for retirement years that ended before September 23, 1996, up to 75 inactive points for retirement years ending on or after September 23, 1996 and before October 30, 2000, and up to 90 points in the retirement year that includes October 30, 2000 and in any subsequent year of service. Points from these sources may be added to points earned from active duty and active duty for training for a maximum total of 365 or 366 points per retirement year. Points are credited on the following basis:

• One point for each day of active service (active duty or active duty for training).
• 15 points for each year of membership in a Reserve Component (Guard and Reserve).
• One point for each unit training assembly.
• One point for each day in which a member is in a Funeral honors duty status.
• Satisfactory completion of accredited correspondence courses at one point for each three credit hours earned.