If you have a balance on your tax account, you’ll get a notice letting you know how much you owe, when it’s due, and how to pay.
If you can’t pay the full amount by that date, you need to figure out what payment options might work for your situation, and act to set up a payment plan or discuss other ways to pay off your balance. Being proactive in addressing the tax debt may prevent additional penalty and interest charges and eliminate the need for the IRS to take action to collect the balance. For specifics, see I got a notice from the IRS.
If your notice indicates you have missing tax returns, file the missing returns as soon as possible. See Filing Your Taxes for more information on how to file your return.