Proration
Proration bills a recurring service for the days it is actually live in a period, rather than a whole period, when it starts or changes part-way through. It keeps mid-month additions and changes fair on both sides without manual adjustment.
Proration is controlled by a single switch, BILLING_PRORATION_ENABLED. With it off, recurring services bill whole periods exactly as before. With it on, the behaviour below applies to new subscriptions and to changes made from that point on. Existing subscriptions are never retroactively re-aligned.
The billing period
System billing periods are calendar months, the 1st to the end of the month. A new company-linked subscription added while proration is on is calendar-aligned: its first charge covers the part-month from the day it was added to month end, and every month after that is a full calendar month billed at the end of the month.
The amount is worked out on calendar days:
charge = round(full period amount × days live ÷ days in the period)
So a £30 per month service added on the 16th of a 30-day month bills £15 for that first month (16th to 30th, 15 of 30 days), then £30 a month from the 1st onward. The pro-rata line on the invoice reads, for example, ... (pro-rata: 15 of 30 days) so it is clear why the amount is below a full month.
Adding seats mid-month
When seats are added part-way through a month, the new seats are pro-rated for the remaining days of that month. The seats already on the service still bill the full month, so nothing is double-charged. A separate pro-rata line shows the added seats and the days they cover.
Reducing seats mid-month
How a reduction is treated depends on when it takes effect, which the service's billing rules decide:
Most services can only be reduced at the anniversary or the next period. In that case there is no mid-month credit, the seats keep billing until the period ends, and the lower count simply applies from the next period.
An exceptional immediate reduction (taking effect mid-month) raises a pro-rata credit for the unused remainder of the month. The credit nets against the next invoice.
A full removal of a service is handled by the cancellation flow, not as a mid-month credit.
What proration applies to
New company-linked subscriptions added while the switch is on. This is the native billing path concorbit uses for its own customers.
Mid-period seat increases and decreases on those subscriptions.
It does not apply to existing subscriptions created before the switch was turned on, to trialing subscriptions, or to services billed through Autotask (Autotask remains the billing source of truth for those).
Checking the impact before turning it on
Run the impact report to see which services would be affected before enabling proration:
php artisan billing:proration-impact
It lists, read-only, any recurring line whose next charge would be pro-rated, with the full and pro-rated amounts side by side. For most existing data it reports no change, because proration never re-bills history, it only affects new mid-period starts and changes going forward.