I say the cost basis is $10.45 per share. According to IRS Publication 550 Investment Income and Expenses:
If a put you write is exercised and you buy the underlying stock, decrease your basis in the stock by the amount you received for the put. Your holding period for the stock begins on the date you buy it, not on the date you wrote the put.
If the cost basis on the 1099-B is reported to the IRS and you want to adjust it, after entering the transaction where you can indicate that the cost basis is incorrect and adjust it.
Was this part of a complex option strategy, or did you simply sell/write a put on the underlying stock?
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