I am doing my father's taxes for the first time this year and am having trouble figuring out the taxable amount from his OPM annuity. Since box 2a is "unknown" and there is an amount in box 9b, I know I have to figure out the taxable amount. However, it appears I can't use the Simplified method because he retired in 1984. Looks like he was supposed to use either the 3 year rule or or the general rule. Do I need to see if he still has his returns from the 80's to see what he did or is there an easier way? Last year he incorrectly(?) used the Simplified method.
I used the simplified method in my initial pass and got a correction message in the review portion because of the start date being earlier than 1986. Appreciate any help.
