Re1099-R for a company pension plan, not an IRA, just pension plan payments. Box 1 has gross distr amt, box 2a taxable amount blank, box 2b tax amt undetermined checked.

[wiessler]

Instructions for choosing taxable amount simplified method or general rule do not address a simple pension plan. Unclear on how to proceed.

[MaryK4]

A simple pension plan generally uses the simplified method because it is a qualified plan.  See The general rule and the simplified method.