How a billing cycle works
Every recurring price has a billing period: monthly, quarterly, annual, or any other length such as every 2 weeks. At the start of each cycle (or at the end, if you bill in arrears), an invoice is generated for that cycle and the customer is charged. Then the next cycle begins.
The billing anchor is the date the cycles line up on. Most subscriptions anchor on the day they started, which is anniversary billing: sign up on the 14th and you renew on the 14th. Calendar billing anchors everyone on the same day instead, usually the 1st. After a free trial, the anchor is usually the day the trial ends.
Month ends need a rule. A subscription anchored on the 31st has no 31st in February or April, so it renews on the last day of those months and returns to the 31st when the month has one.
Worked example
A customer subscribes to a $50 monthly plan on January 31, 2027. The anchor day is the 31st, and 2027 is not a leap year.
- January 31: first cycle starts
- $50.00
- February 28: no 31st, so the last day of the month
- $50.00
- March 31: back to the anchor day
- $50.00
- April 30: no 31st again
- $50.00
- Charged over four cycles: 4 × $50
- $200.00
The anchor stays the 31st even when a short month moves one renewal earlier, so the dates never drift to the 28th for good.
Why the billing cycle matters
The cycle decides when customers are charged, what each invoice covers and when revenue arrives. Proration, trials, renewal reminders and reports all count from it, so a wrong anchor spreads errors everywhere.
It also shapes cash flow and customer experience. Annual cycles bring cash in up front; monthly cycles are easier to start. Invoices that land on a predictable day are easier for customers to approve and pay.
Common mistakes
- Letting month ends drift Adding one month to January 31 by counting days lands in March. Clamp to the last day of short months and keep the original anchor.
- Confusing the billing cycle with the contract term A customer can pay monthly on a 12 month contract. The cycle is how often you charge; the term is how long they committed.
- Changing the anchor without a transition rule Moving a customer's billing day leaves a short gap between the old date and the new one. Decide how that gap is charged.