There can be only one installment agreement that includes all the tax years in which you owe an outstanding tax debt. A new tax balance due would automatically default on your existing installment agreement. To reiterate, you cannot have two installment agreements with the IRS. However, you can pay off more than one tax debt by paying your current installment payment.
If you owe more money to the IRS than you can afford in a lump sum, an IRS payment plan or installment agreement (long-term payment plan) helps you settle your tax debt and avoid aggressive tax collection efforts, such as federal tax levies and wage garnishments..