That will always depend on where you live. As with most contracts I presume you are paid a gross salary by contractor and you deal with taxes and other deductions in your home country. In some countries you will need to pay in social security payments (or equivalent) plus taxes. In some you only have to pay taxes. Some countries gives you the right to make tax deductions depending on marital status, number of children, wife's / partners income etc etc. In other words, net salary will vary widely depending on your personal circumstances.