On the W4 you can write "Exempt" under line 4c and they will not take any taxes out for the federal taxes due. Be warned that if you owe money at the end of the year because of this there may be penalties and interest added to your tax return.
On the IT-2104 you can't claim an exemption. You have to file an IT-2104-E for that. In order to file that you have to certify that you will not owe any taxes to New York for the year. Again, claiming an exemption and then owing will result in penalties and interest being added by New York.
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