When you receive an invoice from us, it could be hard to understand how the amount due is calculated because it has all these "Remaining time" and "Unused time" records. To power our billing and invoicing, we use Stripe payment infrastructure, which prorates the amount due when the number of activated users on your account is changed. It creates the records mentioned above in your invoice.
Here is how the amount due is calculated:
The amount in negative, or tagged as "unused time" is an available amount you can deduct from outstanding unpaid dues (remaining time).
For example, unpaid due is $100.00 and unused time is $75.00, you then will only have to pay $25.00.
Add all the remaining time amount, then add all the unused time amount. Then deduct the sum of all unused time from the sum of all remaining time.
Invoice with proration example
In the above example, $5.06 is the total amount due for the new billing cycle (May 17th-Jun 17th), from which:
$4.50 - the total cost of the activated users created on your Ringotel account at the start of the new billing cycle (May 17th)
$0.56 - the prorated amount for the previous billing cycle, so when you create users in the middle of the billing cycle, it will reflect the future invoice.