## Zoho Billing - Product, solutions, integrations, support, and resources Index

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# How does reference number work? Can it be displayed in email notifications?

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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.