Hello Umair,
Greetings !!
Currently in Pabbly Subscription Billing, the renewal payable invoice is generated for custom payment gateways when the recurring subscription reaches the renewal stage. This renewal invoice is generated & sent to the customer on the day of subscription renewal date .Customers can use this payable invoice to pay for their recurring subscription, thereby renewing it.
The renewal invoice is sent on the day of subscription renewal. It's not possible to send or generate the renewal invoice before 'X' days, as the subscription will still be in the live phase and an invoice can't be generated.
If you wish to keep your subscription live even after the recurring billing date, you can use the 'Payment Term' option to extend the subscription status based on the payment terms. This payment term option can be found in Product > Plan > under the plans you can find the payment term option for that particular plan.