Like so many tax payers, this could happen to you. You get a certified letter form the IRS. When you pick it up from the post office and open it, you read that the IRS intends on levying certain assets.
This means that you have not responded to the IRS's other letters they have been sending you. The IRS can not levy you until you have been through the collection due process. Simply put, they have to notify you of a balance due and give you time to respond.
If you get a CP 504, intent to levy, there is still time to handle your problem.
You do need to get moving right away, because doing nothing will only result in the IRS taking your assets away.
If you are unsure of what steps to take next, it might be time to hire a reputable tax resolution firm. A tax resolution firm can help you out tremendously; they know how to deal with the IRS and can get you back onto the road to recovery and peace of mind.