When I sold stocks last year, I elected net shares tax withholding method. When I filed the 1099-B, I expected my tax refund to increase, but it decreased. Why is this?

Check your Form 1099-B, Box 4 Federal income tax withheld. I

• If you don't see an amount, you didn't have income taxes withheld, or
• If you had income tax withheld, then the taxes withheld, from your trades, was not enough to cover the taxes, from the gain on your trades, when added to your other income.

Helen,

I really appreciate your reply. Box 4 in my 1099-B is indeed 0. I'm surprised that the taxes withheld was not enough to cover the taxes when they withheld around 40% of the shares! Does that sound right to you?

It doesn't sound like any taxes were taken out on the 1099-B.  Did you get any other documentation from the broker?  You should contact the broker and see if they at least intended to withhold taxes.