I uploaded my 1099-B to turbotax installed version.
Proceeds amount is correctly shown but, Gain/Loss amount isn't matching with my 1099-B. Most of my transactions were ESPP and those are the ones that I made manual changes in.
How can I match this Gain/Loss to 1099-B?
Yes, based on the information in box 14 of your W-2, it would appear that your employer has designated your ESPP sale as a disqualifying disposition. Thus, the bargain element, or the discount you received when you purchased the shares has all been included in box 1 or your W-2 because it is taxable as income, just like your regular wages.
Your employer gave you form 3921. Use that to correct basis of each stock on the 1099-B
Because your question relates to ESPP, make sure your cost basis includes the compensation income that was, or should have been, included in box 1 on your W-2. Your 1099-B may not reflect your correct cost basis. For an ESPP transaction, your per share cost basis is the exercise price plus the discount, which in most cases is 15%.
Assuming your gain/loss report reflects your true cost basis, is that cost basis the same as reflected on your 1099-B? If they don't match, then you will need to report the ESPP transactions as they appear on your 1099-B, and in TurboTax you will select the option to make the necessary adjustment to cost basis. After entering the adjustment to cost basis in TurboTax, Form 8949 will reflect that adjustment in column (g).
Thank you @GeorgeM777
I noticed that field 14 Other in my W2 has ESPDD entry/amount.
Is this what you meant when you said its included in my W2 income?
Yes, based on the information in box 14 of your W-2, it would appear that your employer has designated your ESPP sale as a disqualifying disposition. Thus, the bargain element, or the discount you received when you purchased the shares has all been included in box 1 or your W-2 because it is taxable as income, just like your regular wages.