How do I determine the taxable amount, if I do not have the the Total Employee Contribution?

[1-lone-ronin]

I received a 1099-R for an allotment from my ex-husband. The taxable amount is UNKNOWN. I do not know his Employee Contribution.

[MarilynG1]

He may not have made after-tax Employee Contributions to his Retirement Fund, which is the usual situation.

If he did, you may see an amount in Box 5 on Form 1099-R.  If this applies, when you enter the 1099-R, this amount will be subtracted from the Box 1 amount. 

Normally, the taxable amount is the amount in Box 1, even though Box 2 says 'Unknown'.

If you have a CSA-1099-R, make sure you are entering it in the correct section.

Here's more info on Box 2a says Unknown.