annuity taxable amount

[Possi]

It used to be that we used the Simplified General Rule with every annuity. What about a client who has been collecting a death benefit annuity for over 20 years, and box 2 is "unknown." I have been taxing it all.

Now, I see so many other 1099s taxable portion being reduced by Box 5 totals, and box 2 is filled in (taxable portion is reduced by box 5).

I read on IRS site regarding box 5 and it does not say that the taxable portion is regularly reduced by this amount because that figure could be several things that would not necessarily reduce the taxable amount.

Am I right to tax 100%, or should I have been reducing the taxable amount by box 5 all along?

I'm sure it is fatigue that has me second guessing this. I just hate for the IRfrikkinS to get one penny more than they should.