When ISO shares are sold, it's common for the taxpayer to receive both a W2 and a 1099-B. It does not represent double taxation. It's all very well explained in this web reference from Fidelity Investments:
https://communications.fidelity.com/sps_library/docs/bro-tax-sop-iso-click.pdf
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
