Here is what the IRS can do to collect your unpaid tax bill:
File a Notice of Federal Tax Lien.
A lien will attach to property such as your real estate, vehicles, or accounts receivable. The filing of a Notice of Federal Tax Lien puts the public on notice that the government has a claim against your property including property acquired after the date of the notice. Such a lien can harm your credit rating. A Release of Notice of Federal Tax Lien is issued only after your account is settled in full.
Serve a Notice of Levy.
This allows the IRS to seize and sell your property to pay taxes which you did not pay voluntarily. Levies can be made on property you own such as real estate and vehicles. It also extends to property you own which is held by third parties, such as deposits in a bank.
Apply Overpayments.
The IRS can offset any refunds that may be due to you against a prior tax liability still outstanding.