What about if my husband has never filed taxes without his parents? ?

I recently got a yellow letter from uscis saying or better say, requesting my husband to file I-864 himself instead of his parents for me, since he is the petioner. Something I didn't know till now. But the only issue Is I don't know what taxes to send if he has never filed taxes himself other than being in his parents and only last year one! Also he just got this n�w job like 3 months ago where he makes good money. Is there anyway I can replace the taxes with something else like pay tubs or what? We seriously don't know and we really need my EAD To come quick!! Bills are too much for one. P.s WE FILE I-130 & all of them together and already have my biometric for next week.