Will you help me in determining cost basis?

Yes you still need to claim the profit on the sale no matter what you did with the money.

Usually a broker reports net proceeds, so you'd show $1290.05 as sale price if that's what they reported. Your basis would be the $900 you paid plus the $4 purchase commission.

What you do with the money is of no bearing.

Your cost basis is $900 +4.

If you sold for $1300 and the 1099-B shows $1290, you don't add the $9.95 in again. If the 1099-B shows $1300, add the $9.95 to the cost basis.

Calculating and adjusting cost basis accurately is a daunting task, but there is an amazing online tool which will automatically calculate and adjust your cost basis in seconds. It is used by brokerage firms and Fortune 500 companies and is now available to the public. Just go to www.netbasis.com. All you need are the purchase and sale dates and shares of the stock or mutual fund and the system has the rest of the information, such as corporate actions (splits, spin-offs, etc), pricing, and dividends and it also will apply the appropriate IRS rules for inherited and gifted shares. It also provides you with detailed supporting documentation which shows all of the calculations and the adjustments in chronological order. NetBasis also has data going back as far as 1925, so it will accurately calculate cost basis for your old American Telegraph and Telephone shares in seconds.