Do merchants need to send the amount with each charge?
Short answer
No. The merchant sends the customer to checkout with an offer ID. From then on, the platform reads the amount, currency and schedule from the offer and charges each rebill on its date, on the payment method saved at checkout. Your merchants follow every charge in their console.
In detail
No.
One offer ID at checkout
The first payment runs on the hosted payment page, with the customer present. The subscription is created from the offer at that moment.
Rebills read from the offer
Each rebill is a merchant-initiated charge on the saved payment method, with the amount and currency of the offer. There is no billing job to run on the merchant side.
Every charge traced
Each order carries the offer and the version it was billed under, so your merchants and your support teams can explain every amount.