if box 2a on my OPM Form 1099R says UNKNOWN, what should I enter in box 2a? The same no. as in box 1?

[SharonD007]

It depends. If the full amount is taxable, you will put the same number as box 1.

UNKNOWN in Box 2a of your 1099-R means the payer doesn’t know how much of your distribution is taxable so, you’ll need to figure that out when you file your taxes.

In most cases, the full amount is taxable, especially if the money came from a pre-tax retirement account like a 401(k) or traditional IRA.

However, if you made after-tax contributions, part of your withdrawal may be tax-free.

What to do in TurboTax

• Leave Box 2a blank 
• Check “Taxable amount not determined” (Box 2b) 
• Answer the follow-up questions — TurboTax will help calculate it for you 

Quick tip

• If you never made after-tax contributions, you can usually treat the entire amount as taxable 
• If you’re not sure, TurboTax will guide you step by step.

Refer to the TurboTax article Are IRA or pension distributions taxable? for additional information.

[NCperson]

if box 9 is zero or blank, then Box 2a = Box 1. 

However, if box 9 is populated, then follow the directions for the Simplified Method.  OPM is notorius for leaving Box 2a blank when box 9 is populated.