Hello , I receive a monthly survivor benefit ( monthly annuity payments.) from OPM . My annuity start date was June 30, 2012 .

In December 2013 , I received a single net payment that consisted of retroactive “interim” payments (for June 30, 2012 thru Nov 30, 2013 ), equal to 17 retroactive annuity payments.
Federal income tax was withheld from the payment

There is a CSF 1099R Form “STATEMENT OF SURVIVOR ANNUITY PAID” for tax year 2013 for this lump payment.

The 1099R Form states “GROSS ANNUITY REPRESENTS TOTAL PAYMENTS TO ALL INDIVIDUALS UNDER THIS CLAIM NUMBER”

Box 7 distribution code states “DEATH BENEFIT”.
Box 1 shows the “ Gross Distribution” amount.
Box 2a Taxable Amount states “UNKNOWN”
Box 4 shows the amount of Federal Tax withheld.

I am using the Simplified Method worksheet to calculate the Taxable Amount .
Line 5 of the worksheet says to
“Multiply Line 4 by the number of months for which this years payments were made”

My Question is:
What is the correct “number of months for which this years payments were made?

Is it 1 ......because it was a single payment that occurred in year 2013? ...OR

Is it 17 ...because the single payment consisted of 17 retroactive monthly annuity payments ? OR

Is it 11 ...because the payment contained 11 monthly annuity payments allocate for year 2013 ?


Thank You .