Retirement tax questions

I see your reply:

"Withdraw the excess next year. If you don't do one of the other options first, you can withdraw the excess funds by Dec. 31 of the following year. You can leave the earnings in, but you must remove the entire excess contribution to avoid that 6% penalty for the following year."

 

My question is when do withdraw the excess in the next year, is the withdraw taxable? Which year's income?