For an injury accident settlement, do I figure my lost income by gross wages or my net wages?

The settlement should be based on your gross wages, since the settlement is taxable--i.e. if you base it on your net wages, you will be taxing yourself twice, in effect. Furthermore, your gross wages are what you are paid for your work--it is what you are missing out on or not receiving, when you can't work for some time due to an injury.

In any settlement, it is not inappropriate to take a "haircut" from what the plaintiff could win, were he or she to go to trial and win full damages; that is because by settling early, the plaintiff will be paid sooner (and get the time value of money) and save on legal and other litigation-related fees. So you initially use the gross to give you a baseline figure, but expect you will be offered something less than that due to these factors.