If you owe money to the IRS, you will receive a consistent stream letters that become progressively more threatening. There is one letter, in particular, that may be the most important one you receive from the IRS. If you agree with your liability but have not yet paid it, this letter is titled "Final Notice of Intent to Levy and Notice of Your Right to a Hearing" ("Final Notice"). Do not ignore this letter or else you will soon find your bank account empty and your wages garnished. The other important letter is the "Notice of Determination" which gives you 90 days to petition the Tax Court in order to dispute your liability.
What does the Final Notice" mean? Lets go back to the beginning. When you initially owe money to the IRS and your rights to dispute your liability in Tax Court have expired, you will receive a notice stating something along the lines of "according to our records, you have an amount due on your income taxes." This notice will encourage you to pay your balance in full or set up an installment agreement. This notice is polite because, at this time, your account with the IRS is not yet in Automated Collections. Collections is the branch of the IRS that deals with actively collecting a liability due from taxpayers. If you do not respond to this notice, you may receive several other notices prompting you to pay. Again, even though these notices appear increasingly more threatening, your account is still not in Collections. Eventually, you will receive a notice titled "Intent to Seize your Property or Rights to Property" ( CP-504). The CP-504 is your final notice before your account is transferred to collections. If you don't pay the amount due, the IRS may seize your state tax refund and file a Notice of Federal Tax Lien on your property.
This is also the notice before the IRS sends you your Final Notice. When you receive the Final Notice, you have to request a Collection Due Process Hearing ("CDP Hearing") by filing out and sending in Form 12153 (please read this form carefully when you are filling it out). When you request a CDP Hearing, the IRS will assign your account to an agent who will contact you directly through the mail or phone in order to set you up on an installment agreement or, if you are experiencing hardship, place you on Currently Non-Collectible Status ("CNC"). Otherwise, if you ignore this notice, there are no more protections between your assets and the IRS. The IRS can and will go after you.
In conclusion, when you receive mail from the IRS: read it and look carefully for any deadlines that the IRS has imposed. If you don't, you may be in for a much bigger hassle then you orginally thought.