If the bill is not paid or satisfactory arrangements are not made, the IRS begins enforced collection action, including wage levies, bank levies, property seizures and tax liens.

Respond to the notices timely and properly. Collection notices refer to taxes that are currently assessed. Generally, they involve back tax debts. You cannot ignore these notices. If you do not respond to the initial notice seeking payment, the IRS sends a series of further, more harsh demands. The culmination is a final notice, notice of intent to levy, IRS Letter 1058. This states you have thirty days to pay in full or enforcement may begin. The IRS is not kidding. It will enforce collection with all tools available if you do not address the problem.
Always respond to the first notice. Do not wait until the cycle has run to the final notice. Respond in writing, not by phone. Explain that you do not have sufficient income or assets to be able to pay in full. Explain that you need an installment agreement or even uncollectible status if you cannot afford any payment at all. Ideally, you should send a copy of Form 9465, Installment Agreement Request, with your letter. Enter the amount of monthly payment you can afford. As I explained in my discussion of Problem 5, this sets the wheels in motion to establish a formal installment agreement. Once that agreement is in place, the IRS is foreclosed from enforcing collection as long as you meet the terms of the agreement.