Are you receiving retirement benefits from the Teachers Retirement System of Georgia? If you were a teacher, you would have contributed to TRS from your paycheck when you were working. And those contributions were not included in your federal taxable income in those years.

But Georgia was different.Between July 1, 1987 and December 31, 1989, Georgia did not adopt conformity to federal law regarding deductions for contributions to the Teacher Retirement System of Georgia. The state taxed you on those contributions.

Now, Georgia allows a subtraction from your retirement income equal to the contributions made from July 1, 1987 through December 31, 1989 that were not deductible by Georgia. It's a one-time deduction, as retirement plan distributions are received, of previous nondeductible plan contributions.

If you weren't a teacher, or you didn't work as a teacher during those dates, then you don't have any amount to enter. If you did, you'd have to check with your plan administrator to find out the amount to deduct.

What is the one time deduction amount? How do you figure the one time deduction amount?

The one time deduction amount is an amount equal to the amount of contributions to the Teachers Retirement System of Georgia made by a taxpayer between July 1, 1987, and December 31, 1989, which contributions were not subject to federal income taxation but were subject to Georgia income taxation.  

See Georgia Department of Revenue Informational Bulletin IT 2010-06-15 here.

The deduction may be entered at the screen Teacher's Retirement in the Georgia state income tax return.

@straylor1