Billing periods define when customers are charged. Understanding how they work helps you manage subscriptions effectively and answer customer billing questions.
A billing period is the time span covered by a single invoice. At the end of each billing period:
Billing intervals are set per price and can be customized to fit your business needs. While common intervals include daily, weekly, monthly, and yearly, Gilbert supports any combination of count and unit.
| Interval | Period Length | Example |
|---|---|---|
| Daily | 1 day | Jan 1 → Jan 2 |
| Weekly | 7 days | Jan 1 → Jan 8 |
| Monthly | ~30 days | Jan 1 → Feb 1 |
| Yearly | ~365 days | Jan 1 → Jan 1 (next year) |
You can also create custom intervals like 2 months, 3 weeks, or 6 days by configuring the interval count on your price.
The billing anchor is the reference date that determines when billing periods start and end. By default, the billing anchor is the subscription start date.
If you start a monthly subscription on January 15, billing dates will be the 15th of each month: January 15 → February 15 → March 15 → April 15.
When the billing anchor is on a date that doesn't exist in all months, Gilbert uses the last valid day of the target month. This can cause the anchor to drift over time.
For example, if a subscription starts on January 31:
| Period | Start | End | Notes |
|---|---|---|---|
| 1 | Jan 31 | Feb 28 | February doesn't have day 31 |
| 2 | Feb 28 | Mar 28 | Adding 1 month to Feb 28 |
| 3 | Mar 28 | Apr 28 | Anchor has drifted from original day 31 |
Once the anchor shifts to an earlier day, subsequent periods continue from that new anchor.
For monthly subscriptions, the charge is the same regardless of the actual number of days in the month. A February charge (28 days) is the same as a January charge (31 days).
For yearly subscriptions, the billing date advances by one year each period. Leap years are handled automatically—if a subscription starts on February 29, the next billing date will be February 28 in non-leap years.
When a billing period ends:
Several events can happen during a billing period, including plan changes, quantity adjustments, pausing, and cancellation. These can be applied immediately (with proration) or scheduled for the end of the period.
See Subscriptions for details on managing these changes.
Trials work alongside billing periods. If a 14-day trial starts on January 1, the trial ends on January 15, and the first billing period runs from January 15 to February 15.
During the trial:
Invoice dates explained:
| Date | Meaning |
|---|---|
| Issue Date | When the invoice was created |
| Due Date | When payment is expected |
| Period Start | First day covered by this invoice |
| Period End | Last day covered by this invoice |
Monthly billing charges the same amount regardless of whether the month has 28, 30, or 31 days. This is standard practice and matches customer expectations.
No; the billing anchor is set when the subscription starts and remains fixed. This ensures predictable billing dates.
The billing anchor cannot be changed directly. The only options are to start the subscription on the 1st, or make a change on the 1st that triggers proration—which resets the anchor to that date.
If your annual price isn't exactly 12× the monthly price (e.g., monthly at €29/month = €348/year, but annual at €290/year for a €58 savings), create separate prices for each interval.