Proration
Proration is the billing calculation applied when a subscriber changes their subscription plan (upgrades, downgrades, or pauses) mid-billing-cycle. Instead of charging a full period for both the old and new plan, the billing system calculates the prorated credit for the unused portion of the old plan and the prorated charge for the new plan’s remaining days.
How it works — a worked example
A subscriber on a $100/month plan upgrades to a $200/month plan on day 15 of a 30-day billing cycle.
- Old plan unused: 15/30 days Ã- $100 = $50 credit
- New plan remaining: 15/30 days Ã- $200 = $100 charge
- Net charge at upgrade: $100 - $50 = $50
At the next billing cycle renewal, the subscriber pays the full $200/month.
The three proration methods
1. Day-count proration (most common): charges/credits based on exact calendar days. Standard in Chargebee, Recurly, and Stripe Billing.
2. Billing-cycle proration: splits the cycle into equal parts (e.g., 4 weeks regardless of actual days). Less common; can create confusion for monthly subscribers in months of different lengths.
3. No proration (immediate full-period charge): the new plan is charged in full at upgrade and the old plan is not credited. This is hostile to subscribers and drives upgrade friction. Acceptable only for very low-cost products where the proration calculation overhead exceeds the credit amount.
Why proration matters for subscription LTV
Proration directly affects subscriber willingness to upgrade:
- Visible proration: showing the subscriber exactly what they owe and why before the upgrade confirms increases upgrade conversion rate by 15–30% (internal data from Recurly’s customer portal benchmarks)
- Hidden proration: charging the prorated amount without explanation generates more payment disputes and reduces upgrade confidence
- No proration: creates upgrade friction — subscribers wait until their next billing cycle to upgrade, delaying revenue
Recurly’s customer portal shows proration calculations in real time before the subscriber confirms a plan change. Chargebee’s portal shows the calculation but the UX is less polished. Stripe Billing calculates proration correctly but the default checkout doesn’t display the calculation clearly.
Edge cases billing platforms must handle
Annual to monthly downgrade: subscriber moves from $1,200/year (paid upfront) to $100/month. The platform must calculate the unused annual credit and apply it to future monthly invoices — potentially covering many months before new charges appear.
Mid-cycle quantity changes (seats): a B2B SaaS adding 3 seats mid-month gets a prorated charge for those seats’ remaining days. At scale, with frequent seat changes, this creates a complex proration schedule.
Trial to paid: no proration applies — the trial period is free and the first charge is for a full period starting at trial-end.
Currency differences: international subscribers on multi-currency billing require proration calculated in the original currency, not converted mid-calculation.
Platform comparison
| Platform | Proration display to subscriber | Proration accuracy | Edge case handling |
|---|---|---|---|
| Chargebee | Shown at upgrade, not pre-upgrade preview | High | Strong — handles annual/monthly mix |
| Recurly | Real-time preview before confirmation | High | Strong — best portal UX for plan changes |
| Stripe Billing | Calculated correctly, not displayed by default | High | Requires custom UI for display |
| Paddle | Shown in checkout overlay | High | Good for standard cases |
The difference between platforms is not the calculation accuracy (all four are correct) — it’s the subscriber-facing UX that determines whether proration drives upgrade confidence or upgrade friction.