> ## Documentation Index
> Fetch the complete documentation index at: https://support.effra.io/llms.txt
> Use this file to discover all available pages before exploring further.

# How do I use card on file?

Effra's card on file feature allows you to collect patient card details and charge them automatically if they need to pay a shortfall payment.

Payment details are stored securely with Stripe and are never shared with you or Effra.

For new patients you should share a generic link with them as part of your registration process.
The link can be found at the top right of the [patients page](https://app.effra.io/patients) in the dashboard.
Patients will be guided through the process of saving their card details.

For existing patients you can share a specific link with them that will take them to the card on file page.
The link can be found in the patient's page in the Effra dashboard.

When a patient owes a shortfall payment, they will be sent an invoice on the day it is raised and then charged automatically on the due date.

The due date is 5 days by default (D+5), but can be configured to 7 days (D+7).