Partial Payment

Partial Payment enables patrons to pay using other payment options alongside Centrapay.

Partial Payment is a core feature of Centrapay’s payment protocol. Integration is required to allow acceptance of Centrapay Assets that relate to specific Line-Items such as Tokens.

This offers a practical solution for point of sale systems to support three different experiences, including merchant driven and app driven partial payments or a hybrid of both.

Following the implementation guide below will enable all three supported scenarios.

Partial Payment Flow

    sequenceDiagram
autonumber
	opt
		Patron->>POS: Make external payment
	end
	POS->>Centrapay: Create Payment Request (with partialAllowed = true)
	par
		Loop Starts polling for Payment Confirmation
			POS->>Centrapay: Get Payment Request
		end
		POS->>Patron: Connect with Patron
		Patron->>Centrapay: Makes a Payment
		note over POS: Stop Polling for Payment Confirmation
	end
	opt remaining amount > 0
		Patron->>POS: Make external payment
	end
	note over POS: Display Confirmation
  

Merchant Driven Scenario

A patron asks the merchant to process a specified part of the total basket amount using Centrapay. This could be due to the patron knowing their Centrapay Asset balance wouldn’t cover the complete basket amount or enable them to use a set amount of funds from a fixed value asset eg. Token to complete the payment. Related steps in diagram above: 1→2→3→4→5 or 2→3→4→5→6

Patron Driven Scenario

A patron using a mobile wallet app may find they lack enough funds to cover the full payment after connecting to a Centrapay Payment Request. Instead of the cashier needing to cancel the Payment Request and start over, the patron can make a partial payment with available funds. Once the Centrapay payment is successful, the point of sale can take payment for the remaining amount using another method. Related steps in diagram above: 2→3→4→5→6

Hybrid Partial Payment Scenario

A combination of Merchant and App driven partial payments to cater for edge cases where needed. Related steps in diagram above: 1→2→3→4→5→6

Implementation

Creating the Payment Request

When creating a Payment Request , opt into partial payment by:

• Setting partialAllowed to true.
• Setting value.amount to the amount payable via Centrapay.
• Setting basketAmount to the total amount of the transaction, including external forms of payment, e.g., cash or card. This value should be equal to value.amount if the patron is completing their entire transaction using Centrapay.

If the patron has paid by another method or indicates they would like to pay a part the transaction with Centrapay, then value.amount should be less than the basketAmount.

If you are integrating with the Line Items payment extension , the total amount of line items must sum to either the basketAmount or the value.amount.

Polling for Payment Confirmation

Continue to poll the status of the Payment Request until it is no longer new. If the Payment Request status has been updated to cancelled or expired, proceed as you normally would. If the status is paid you need to check the remainingAmount property on the Payment Request.

• If it is 0, then the entire amount requested via Centrapay has been paid.
• If it is greater than 0, you will need to request the remaining amount from the patron via another payment option. If the patron cannot complete the transaction then the payment request should be refunded .

See also

• Point of sale