You will have notice and some time to pay or otherwise deal with the tax debts. The IRS always sends a bill first. That bill will be based on your tax return and will likely include appropriate interest and penalties.
You will always receive at least a second bill before the IRS begins collection efforts.
Do not simply ignore these invoices. Instead, get professional advice regarding your options for dealing with these tax debts. The earlier such problems are confronted, you will generally have more options available.