What is the proper way to adjust the cost basis for the SLV / GLD ETFs that are structured as trusts, and have monthly expenses that show up on your 1099-B?

You can adjust the cost basis of an investment sale reported on a Form 1099-B when you enter the sales proceeds and cost basis in the Investment Income section of TurboTax. You do that by clicking on the box that says The cost basis is incorrect or missing on my 1099-B. 

 

A couple of screens later you will see an option to enter the correct cost basis:

 

 

 

Thanks for the pointer. How do I get to that screen.  My TT defaulted to a "keyhole" pop-up screen where the number of entries can't be changed, nor could I change the size of the screen.  On this small screen I could not find a way to enter more than one purchase date.

OK I think I've got it:  Never go to the pop-up; Go directly to "Investment income" and enter whatever you know is correct there.