I recently lost my job and collected my 401k which was $18,364 minus 20 % tax ($3, 672) and minus my loan ($ 2,290) which left me with $12,400. How much will I owe once taxes are due again? (I live in PA).

Depends on your tax bracket. That 20% is a down payment on your tax bill - whether you actually owe more, or are due a refund, can't be determined until you figure your taxes. However, be aware that the 10% early withdrawal penalty is NOT part of the withholding, so it's likely you will owe another $1800 or so to the IRS (asuming you are under age 55). And then you have PA income tax on the $18,364 - assuming that you are under age 59-1/2, PA taxes the distributon to the extent that it exceeds your own employee contributions. This is because you've already paid PA income tax on our own contributions, since PA - unlike all other states - taxes employee contributions to 401(k) and IRA plans. Your plan administrator should be able to tell you how much of the distribution you took is taxable by PA.