The calculation of the amount of social security benefits subject to tax is governed by section 86 of the Code and is fairly complex. (investinginbonds.com)
How can one just retire after 10 years of work and be eligible for social security benefits for the rest of their life? (money.stackexchange.com)
Example: You decide to begin receiving social security benefits in 2004, but you will not reach full retirement age until 2006. (fairmark.com)