Installments system and method

A computer-implemented method, performed by a network computer managing a plurality of Application Programming Interfaces (APIs), the method comprising:

• transmitting, by the network computer to a merchant computer, a first key for accessing an eligibility API of the plurality of APIs and a second key for accessing an authorization API of the plurality of APIs;
• receiving, by the network computer from the merchant computer via a call to the eligibility API, a request message for an installment plan, the request message comprising transaction data for a transaction with a user, the transaction data including an account identifier for an account of the user, a total amount for the installment plan, and the first key or a derivative thereof, wherein the transaction with the user was initiated by a user device transmitting the transaction data to the merchant computer;
• determining, by the network computer, that the transaction is eligible for the installment plan by analyzing the transaction data;
• based on determining that the transaction is eligible for the installment plan, transmitting, by the network computer via the eligibility API, data identifying the installment plan;
• receiving, by the network computer via the eligibility API, acceptance of the installment plan by the user, wherein the user selected and approved the installment plan via an installment interface;
• receiving, by the network computer from the merchant computer via a call to the authorization API, an authorization request message for the transaction, the authorization request message comprising an identifier of the installment plan, the total amount, and the second key or a derivative thereof;
• responsive to confirming the acceptance and receiving the authorization request message, transmitting, by the network computer to an authorizing computer, the authorization request message for the total amount, thereby causing authorizing and clearing of the total amount;
• transmitting, by the network computer to the merchant computer, an authorization response message comprising an indication that the installment plan has been initiated, the total amount, and an installment amount, thereby causing the merchant computer to provide installment information comprising the total amount and the installment amount to the user;
• creating, by the network computer, a temporary account for the installment plan and an identifier for the temporary account for the installment plan;
• recording, by the network computer, the total amount to the temporary account associated with the identifier for the temporary account;
• and
• processing, by the network computer, an installment from the temporary account, thereby decrementing the temporary account by the installment amount, wherein processing the installment from the temporary account comprises:
• transmitting, by the network computer to the authorizing computer, a first installment authorization message comprising a first amount, wherein the authorizing computer blocks a credit line of the user based on the first amount;
• and
• transmitting, by the network computer to the authorizing computer, a second installment authorization message comprising a second amount, wherein the authorizing computer blocks the credit line of the user based on the second amount.