Cost Basis is Blank on 1099-B

Forum|Forum|4 months ago
April 13, 2026
3 replies
206 views

My broker can't help me, and I don't have records from about 10 years ago when I bought SOME of this mutual fund. Now that I sold it, I am having problems with PART of it (they divided it into two separate 1099-Bs)... One is just fine with ALL the data I need. But, the other part has nothing for the cost basis. My broker says it's a noncovered security where cost or basis is unknown. HELP - I don't know what to do at all ! -Dave

AmyC

Level 15

Brokerages keep track of things now days. In the past, a brokerage was not required and brokerage buy outs often lost track if they did know.

You have two forms, one for required bookkeeping and one for before those years - phase in was 2011-2014 depending on the security.

The unknown tells me it was years ago. You have two options:

claim zero basis and pay tax on the whole amount
determine a best effort estimate:
- look for reinvested dividends - each share increased your cost basis
- check historical prices
- check the mutual fund company - the broker might not know but the fund might, you can call shareholder services.
- make a reasonable estimate and make note of how you determined it
- any basis beats no basis

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SuperDave8833Author

Level 2

Hi Amy C - I've done a lot of research on the internet. Does this seem right... I'll check box E - Long-term basis not reported to IRS, I'll leave the cost basis box blank, but when it asks "Do you have adjustments to this investment sale?" I will check "Yes", And then I'll check the box for "The basis shown in Box 1e is incorrect." The next page will ask for the correct basis amount, which I can accurately guess by historic fund price ??? Am I even close ?

AmyC

Level 15

As long as the actual information on the tax page is correct, how it gets there is irrelevant. The program sends the tax pages. You can use it on the main page or the corrections (really for when the broker is wrong). As noncovered, I would use the main page for ease.

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