Can the Merchant Order ID (merchantPaymentId) be duplicated?

Basically, please consider implementing a merchant order ID (merchant_order_id) that is unique to each merchant (merchant ID).
PayPay also confirms the uniqueness, but only when the following conditions are met, the uniqueness check for the same merchant order ID will not be performed.
In the unlikely event that it is issued, the result of multiple records will be returned when querying the reference API. In that respect as well, we strongly recommend that you revise it so that it is unique.
<Condition>
・When the same user with the same member store ID makes a payment with the payment method after any of the following periods
・921 days or more: Credit card payment or deferred payment
・More than 525 days: payment method other than the above