Credits are based on the amount of your earnings. You can earn up to a maximum of 4 credits each year when you work in a job or operate your own business as a self-employed person and pay Social Security taxes.

Each year the amount of earnings needed for credits goes up slightly as average earnings levels increase. In 2007, you earn one credit for each $1,000 of your earnings. So if you have earned at least $4,000 during the year, you get the maximum 4 credits.  In 2006, the amount for one credit was $970.
 
The credits you earn remain on your Social Security record even if you change jobs or have no earnings for a while. Social Security uses your work history to determine your eligibility for retirement or disability benefits or your family's eligibility for survivors benefits when you die.