You may utilize InterPayments API as state management for the NICN value. This is useful when you have multiple pages or progressions during your e-commerce flow.
The NICN, Amount, and Region are not readily available to call the API endpoint all at the same time. InterPayments will maintain the NICN across calls.
When the Amount and Region are available, the NICN will not be required for that call, and will be used from the previous endpoint calls. In order to find the current state of a NICN, the sTxId or mTxId is mandatory for locating and transitioning state.
A NICN passed in without a Region or Amount will be stored for later use. For later use, a sTxId or mTxid along with a Region and an Amount is required to complete the workflow.