what is the maximum # amt you can claim on your w-4 form?

Answer 1

Officially there is no limit. But if you put down 20, cut your withholding way down and then owe more than $1000 at tax time, the IRS may send your employer a lock-in letter limiting you to S/1 or S/0.

Answer 2

You can legally claim whatever you are entitled to in order to break about even at the end of the year.

vb is correct on what happens if you illegally claim more than you are entitled to. You'll also end up paying a penalty for underwithholding.