# Billable and internal time

> What the billable flag does, where unbilled time collects, and why invoiced entries are locked.

Every time entry is either **Billable** or internal. The flag decides whether the hours can reach an invoice.

## Billable

- Billable entries collect on the project as **unbilled time**. The project's Billing tab and My Work show the total.
- When you bill the project or the retainer period, every unbilled billable entry of the period is collected into the invoice. See [Bill a project](/help/billing/bill-a-project/).
- The rate comes from the entry's captured rate, the service, the person, the project or the rate card, in that order. See [Rate cards](/help/settings/rate-cards/).

## Internal

Internal time is logged against a project or against internal work, counts for utilization and capacity, and is never invoiced. Set the project's billing type to **Non-billable** if a whole project is internal.

## Locked entries

Once a time entry is part of a finalized invoice, it is locked. You cannot change its duration, project or flag, so the invoice and its statement of hours always agree. Correct the invoice with a credit note instead, see [Invoices](/help/billing/invoices/).

## Changing the flag later

Open the entry and switch **Billable** off or on, as long as it is not locked. At month end, that is how you decide what reaches the invoice.