1099-B reported and not reported does not match supplemental data. what do I use

[Tony91646]

I have a 1099-B with sections "reported to IRS",  "not reported IRS" and "supplemental data" from a large brokerage company.      There is RSU, ESPP, and possibly NSOs in the list.     They are all long term gains.

I can match up 4 of the 5 of the not reported to IRS and maybe 2 out of the 6 of the reported to IRS with the supplemental data based on number of stocks and approximate date.   The rest of them are not even close to what I can find in my account history.   The total proceeds are the same

What path should I follow to fill in my taxes?   Do I follow everything in supplemental data even though the total in wash sales, gains, etc do not match the lines in what is reported and not reported.    or do I remove all the supplemental data and follow the data for the what is reported and what is not reported and attempt to fill in the basis there.    The 3rd option which I tried but might try again is call the brokerage house and try to determine why there is a big difference in line items.

[ReneV4]

The proper path for you to take with regard to your Form 1099-B and the supplemental data is to use both. Do not rely solely on one or the other because both are needed to find your true cost basis so that you don't overpay taxes.

To simplify, you do not need to match line items exactly. You need the total proceeds to match your Form 1099-B and you need your total adjusted basis to match your supplemental data.

First, enter all of the information provided on Form 1099-B as it appears on the form. Even if some of the cost basis is showing as zero (0) and you know this to be incorrect. The important thing is to make all of the entries so that what appears on your Form 8949 and Schedule D reflects exactly what was reported on the 1099-B.

Next, you will need to make the necessary adjustments by selecting the, "I need to adjust my total cost basis" box found just below the box where you enter the Total cost or other basis.

You can select from the boxes with different codes that appear, including for the wash sales you mentioned (Box W).

When making the adjustments, you will enter the differences between what was reported on the 1099-B and what is reported in the supplemental data.

As for your third option, it is a good idea to call the brokerage to ask about the big differences in the line items. The information they provide may help with your adjustments.

[Tony91646]

I talked to the brokerage house and needless to say they were not much help.     They indicated because of wash sales. it is complicated.   They also indicated it is a known back end issue of some sort. 

The short/long of it is 

The 1099 "is reported" to government has "lots" that do not show up in the supplemental data

What is the best way to solve this issue?

The 1099 "is not reported" to governmnent has at least 1 lot that does not show up in the supplemental data.

TurboTax pulled in the "supplemental data" but since the lot sizes/proceeds do not match up 1 for 1 with what "is reported" and "what is not reported".   Some of them are not even close.  I am unable tell Turbo tax what is reported and what is not reported.  so when i send my taxes in,   I am guess I will be flagged because what the 1099-B says is reported and what I say is "reported" do not match up at all. 

I think the suggested I received from ReneV4 is...  just want to make sure I heard correctly...

I could just input what is "reported" and what is "not reported" as the 1099-B verbatim and adjust cost basis as best as I can for data that matches.     Would that reduce my chances of being flagged?