No you cannot include the cost basis for the shares you sold in 2017 in the cost basis for shares you sold in 2024 (or any other year). In your example, your cost basis is $10 per share and that is what you have to use for your remaining share. Form 3115 would not apply to this situation. This is not a change in accounting method. Your remedy would have been to file an amended return, but it is too late to file an amended return and receive a refund for a timely filed 2017 tax return.
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