Proration
Adjusting a charge to match the portion of a billing period actually used, such as when a client starts or changes plans mid-cycle.
Definition
Proration means adjusting a charge so the client pays only for the portion of a billing period they actually use. It shows up whenever something changes mid-cycle: a client starts a $1,200/month retainer on the 16th of a 30-day month, so the first invoice is $600 for the remaining 15 days; a subscriber upgrades halfway through the month and owes the price difference only for the days remaining.
The standard mechanics are daily: divide the period price by the number of days in the cycle, then multiply by the days at each rate. On upgrades, billing systems typically issue a prorated credit for the unused portion of the old plan and a prorated charge for the new plan through the end of the cycle, netting them on the next invoice. Downgrades and cancellations raise a policy question—credit the unused time, or apply the change at the next renewal—and either is fine as long as your terms say which.
Why It Matters
Proration is mostly about fairness, and fairness is what makes recurring billing feel trustworthy. A client charged a full month for ten days of service starts the relationship annoyed; a clean prorated first invoice signals that your billing is precise. It also removes friction from upgrades—clients say yes faster when they know they will only pay the difference for the rest of the cycle, not a double charge.
The risk is doing it ad hoc. Hand-calculated prorations are a classic source of invoice disputes and awkward credits, and inconsistent policies (crediting one client's downgrade but not another's) can sour relationships. Set the rule once—daily proration, charges and credits netted on the next invoice—write it into your terms, and let your billing system apply it the same way every time.
Examples
- 1
A client joins a $1,500/month retainer on April 21st; the first invoice is a prorated $500 for the final 10 days of the 30-day cycle.
- 2
A subscriber upgrades from a $50 to a $90 plan with 15 days left in the month and is charged a prorated $20 difference at the next invoice.
- 3
An agency cancels a client mid-cycle for non-payment and issues a $400 prorated credit for the unused portion, per its written terms.
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