I have been a green card holder for many years, and always meant to apply for U.S. citizenship. But I was so busy with work and family that I didn't get around to it. Then I lost my job last year and was not able to pay my taxes. I sort of panicked and wasn't sure what to do, so I did not even file a tax return. I would really like to apply for citizenship -- especially because my parents would like me to help them immigrate -- but am now worried about what effect my nonpayment of taxes will have. I've been doing odd jobs, so hopefully will be able to save up money to pay the tax bill soon.
As you probably know, one of the requirements for U.S. citizenship is that you show "good moral character." This doesn't mean showing that you're better than the average person, but it does involve showing that you have behaved well, including paying your taxes. The naturalization application Form N-400 issued by U.S. Citizenship and Immigration Services (USCIS) specifically asks about whether you have paid the taxes that you owe. (See "When Visa or Green Card Holders Must Pay Taxes" if you're in doubt.)
However, missing a tax payment doesn't mean you are forever barred from U.S. citizenship. The important thing now is that you do everything possible to fix the situation. This will most likely involve filing your tax return and including a payment for the basic amount and any applicable penalties. Or, if you still can't afford the full tax bill, you may be able to work out a payment plan with the IRS.
Evidence that the applicant is complying with such a payment plan has, in some cases, been accepted by USCIS as sufficient proof of good moral character.
Still, this is a tricky situation. Your best bet is to get expert help from both a tax professional and an immigration attorney. The immigration attorney, for example, can help you by writing a persuasive letter to accompany your N-400 application, explaining why your failure to pay taxes does not indicate a lack of good moral character. The attorney can also help you collect and present other evidence of your good moral character, for example by presenting letters and documents showing your community involvement, dedication to family, participation in religious worship activities, and so forth.