Eligibility for award, commencing with the period after 31 December 1960, was established by DOD Directive 1348.7, dated 1 April 1966, and terminated effective 15 August 1974, per letter from Manpower and Reserve Affairs, subject: Termination of Eligibility for the National Defense Service Medal, dated 30 June 1974.
If you are single and under age 65, you can earn up to $9,499 in a year and not file a tax return. Should you be 65 or older, you could earn up to $10,949 and be exempt from filing a federal tax return. However, you may qualify for an Earned Income Tax Credit, which is refundable in cash to you.
How much income do you have to earn before you file income tax return as a student?