# Subscriptions
The **subscription is the link between a customer, what products they purchase, and what prices they have agreed to pay.**
Subscriptions can be created manually from the customer page, through automation via pre-built CRM integrations, or using the Plock API.
## Subscription states
* **Active**: Currently billing
* **Draft**: Created but not yet started
* **Paused revenue collection**: Invoicing temporarily stopped — charges still accrue
* **Ended**: Cancelled with an end date
If a customer purchases products with different payment schedules, put them in separate subscriptions.
## In advance & in arrears
Each product in a subscription can be charged either at the start or end of the billing period — independently of other products:
* **In advance**: Fixed fee products are invoiced at the start of the billing period
* **In arrears**: Usage-based products are invoiced at the end of the billing period, after consumption is measured
{% hint style="info" %}
**Tip:** This lets you combine a yearly licence invoiced upfront with usage-based products invoiced monthly at the end of each period — all in one subscription.
{% endhint %}
## Billing interval
Subscriptions can bill monthly, quarterly (every 3 months), every 6 months, annually, or on a custom interval (e.g. every 2 months). Products with different billing schedules should be in separate subscriptions.
## Billing period modes
Two modes control how billing periods are calculated:
* **Calendar month**: Periods align to calendar months regardless of the subscription start date
* **Continuous**: Periods follow the subscription start date — starting on the 15th means each period runs 15th to 14th of the following month
## Renewal anchor date
The renewal anchor date aligns the first billing period to a specific date — for example, the start of a fiscal year. Only the first period is affected; all subsequent periods follow the normal billing interval from there. Useful when onboarding mid-year customers who need their contract aligned to an annual cycle.
## Proration
When a subscription starts mid-period, charges for that first period are automatically prorated — only the portion of the period from the start date is billed.
## Minimum commitment
A subscription can have a guaranteed minimum amount per billing period. If the calculated total falls below the minimum, the minimum is charged instead. Any usage above the minimum is billed as overage.
Invoices are always generated regardless of usage level — minimum commitment sets a billing floor, not a threshold that defers or suppresses invoicing.
## Rebates
Discounts can be applied at both the subscription level and per item:
* **Percentage**: A percentage off the total or individual item
* **Fixed per unit**: A fixed deduction multiplied by quantity
* **Fixed total**: A flat deduction from the invoice line regardless of quantity or usage
* Rebates can have an **end date** — they expire automatically without any manual action needed
## Price indexation
Subscriptions can be configured with automatic annual price adjustments — a date and a percentage. On that date each year, all items in the subscription are increased by the configured percentage. No manual action is needed.
## Cancellation period
A configurable notice period (e.g. 3 months) before a subscription can be ended. This is tracked and visible in the subscription details.
## Cost centre and project fields
Individual subscription items can be assigned a cost centre and project for financial tracking. These fields appear on invoices and can be used for internal cost allocation.
## Group billing
When a master account has child accounts, their subscriptions can be billed together. If billing periods and practices match, Plock consolidates charges into a coordinated billing run. See [Customers](/plock-overview/guides/customers.md) for how to set up account groups.
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