OK, as we all know, for Fidelity we have to put in our cost basis and update it monthly. I am doing that. And I use what Fidelity says on its website, but I don't think it is correct. LOL
In reality, there is no cost basis tax-wise for an IRA because every withdrawal is 100% taxable, so the only reason to know the true cost basis is for evaluating adequately how the investment is doing.
If one is reinvesting the dividends in the IRA, which is what one normally does, doesn't the cost of those reinvestments count as part of the cost basis. I mean you are getting a $100 dividend and then "spending" the $100 to buy more stock or mutual fund. OTOH, you don't report the dividend as taxable so I guess the reinvestment cost you nothing.
The only money you "invested" was your annual contribution, but how can you divvy that up between investments? I am going in circles trying to get my head around this.