The IRS offers the Online Payment Agreement (OPA) Application.
For taxpayers, "paying their taxes in full and on time avoids unnecessary penalties and interest." But, under some circumstances, the taxpayer simply cannot pay their taxes in full, and in this case, may request a payment agreement.
The IRS has stated that for "Individuals who owe $25,000 or less in combined tax, penalties, and interest can use the OPA application to request a payment agreement."
Further, "this application will allow the taxpayer or their authorized representative (Power of Attorney) to qualify, apply for an installment agreement, and receive immediate notification of approval."
The OPA uses the terms installment agreement and payment agreement/plan interchangeably.