Depends on if your ex is decreasing her taxable portion by a proportional share of your cost. If spouse is reporting the entire amount as taxable, I would suggest you can continue allocating your total cost based on the Simplified Method Worksheet value. This should have the effect of lowering your taxable amount as spouse would be reporting 100% of their share as taxable. Now if you gave spouse your total cost and spouse is take reporting a proportional share based on their share of the annuity benefit to the total benefit, then you would need to decrease your total cost on your side to come to the non-taxable year to date. My bet spouse is reporting the full amount as taxable.
Here is a link to the Simplified Method Worksheet. It might help to fill it out by hand to see where you are with the total amount recovered from your original cost.
