It may help to think of the per-share cost basis. If the taxpayer's compensation for 39 shares received = $4,000, then his per-share cost basis is $102.56.
If he then sells 22 of those shares, his cost basis for the transaction is 22 x 102.56, which = $2,256.41.
The cost basis of the original 39 shares is not changed by the fact that some were sold to pay taxes.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
