Documenting the time you miss from work will increase the value of your case significantly. Missed time from work is compensable in itself (you get paid for the time you were off), but also is evidence of a more serious injury. If you were hurt but went to work, it appears (rightly or wrongly) that you were not as seriously injured as someone else may have been.
Check out our wage verification form for an idea as to the type of information that an adjuster (or ultimately, a jury if necessary) will need to see evidence of your wages:
The name and address of your employer
A brief description of your position
How much you make, and how you get paid (hourly, salary, commission, etc.)
The dates you missed from work
The date you went back to work
You will have to prove you have paid your taxes. Be prepared to show a pay stub showing your withholdings or a tax return if a case has to go to Court.