Hi,
If you have missed out to deduct earlier, you can make the deduction now. However, what is important to note here is you have to make estimated salary for full year(Actual salary paid so far + projected salary for balance part of year) an arrive at annual income tax liability and devide the liability by number of years that are there ie., 4 months if you are going to start from this year.
Hope this clarify the first part.
For Professional tax, you will have to deduct on monthly basis and remit to your prof. tax authorities as per local law.
rgds
vishwanath