As an Enrolled Agent, I have the knowledge, skill, and ability to prepare unfiled Form 1040, 1040A, or 1040EZ.
If you owe the IRS for unpaid taxes, generally the IRS will not approve an installment agreement until all unfiled returns have been submitted to the IRS.
The IRS will not accept an Offer in Compromise (OIC) until all income tax returns have been filed.
The IRS charges five (5%) per month for failure to file penalty, but only charges half (1/2%) per month for failure to pay penalty.
Failure to file income taxes could be referred by the IRS to the Department of Justice for criminal proseution. It is rare for the IRS to make a criminal referral, for failure to file income taxes,however, the IRS does have this authority.
In summary, always use a qualified tax professional, to prepare and file your income taxes.