## Zoho Billing - Product, solutions, integrations, support, and resources Index Access the complete documentation index at: https://www.zoho.com/kw/billing/llms.txt Use this file to discover all available documentation pages before proceeding. [Back](./) # How does reference number work? Can it be displayed in email notifications? Reference Number is a custom field that can be filled by the merchant to specify any unique/non-unique identification number or code for a particular subscription. Reference number can be edited at any time during the subscription. It is displayed in invoices and can even be displayed in email notifications by using the email placeholder **%ReferenceNumber%**. The same can be achieved by selecting the **Reference Number** placeholder while editing the email template. Was this document helpful? ![](/billing/images/ue-resources/common/thumbs.svg) Yes ![](/billing/images/ue-resources/common/thumbs.svg) No Was this document helpful? Enter your comments or feedback on this page Enter your email address ![](#) Refresh Type the characters you see in the image above By clicking Submit, you agree to our [Privacy Policy](https://www.zoho.com/privacy.html) . Submit Cancel Submit Submit ![](/billing/images/ue-resources/common/smiley.svg) Thank you for your feedback!