My wife took a contracting job earlier this year but as I'm preparing end of year tax moves, I realized that they have not been taking out taxes (makes sense because she's a contractor) but now I'm concerned about the implications. We had no federal estimated taxes due last year but we did have PA state taxes which I make quarterly. Now that I know we will owe the taxes on her contracting income, should I make a payment (how do I even calculate it) before the end of the year to both the IRS and PA? Will we be hit with a penalty regardless of what we do (pay now or just pay when we file)? Any advice would be appreciated.