Taxed Distributions form an IRA

[nun]

I have an IRA worth $300k with $20k of after tax contributions, I've submitted an IRS 8606
to document the $20k taxed basis. My IRA provider has no way of tracking the taxed money so when I take a distribution the 1099-R will declare the entire distribution taxable. How do I calculate the taxable amount, is it simply 1/15 of the distribution, and how do I claim the tax back?

[MasterBlaster]

On the 1040 form under income you list the IRA distributions. In another spot next to it you list the taxable portion.

The taxable portion is just the ratio of taxed to untaxed balances times the amount you had distributed.

Take a look at a 1040 form