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Custom Fields FAQ

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Last updated on Sep 19, 2026

Answers to common questions about how custom fields behave in Advanced Billing.

How many custom fields can I create?

A site can have up to 100 custom fields per record type, and the limit is counted separately for each type. That means 100 Subscription custom fields and 100 Customer custom fields on the same site. Test sites are limited to 50 per record type.

Creating a field beyond the limit fails with an error naming the limit and the record type. Contact Maxio Support if your site needs a higher limit. For the rest of what custom fields can and cannot do, see Understand Custom Fields.

Can I change what a custom field is attached to?

No. Attached To is set when you create the field, and it becomes read-only afterward. A field created against a Subscription cannot be re-pointed at a Customer.

To move to the other record type, create a new custom field with the record type you want. For the full set of field settings, see Configure Custom Fields.

What happens if I delete a custom field?

Deleting a custom field is permanent. It removes the field from your site and also deletes every value ever recorded for it, across every Subscription or Customer that had one. There's no way to recover the data afterward.

Why don't I see the Display Field Data on Statements option?

Your site uses invoice-centric billing, a billing model that, among other changes, replaces Statements with Invoices. Advanced Billing hides the Display Field Data on Statements option on those sites, and it also drops the matching Statements column from the Custom Fields list and the Statements filter from its search bar.

The other display options are unaffected. Use Display Field Data on Invoices to show the field's data to those customers instead.

Are custom fields included in webhooks?

Not in an ordinary webhook payload. A signup_success or subscription_state_change payload, for example, carries the Subscription, Customer, and Product objects but no custom field data.

You have two ways to reach the values:

  • Subscribe to the custom_field_value_change webhook. It fires whenever a custom field value is added or changed on a Subscription or Customer record, and its payload carries the field name, the record it belongs to, and both the old and new values.
  • Make an API call after receiving any other webhook, to read the current custom field values for that Subscription or Customer.

Use the first if you care about the change itself. Use the second if you need the current values while handling some other event.

To look up the event key and trigger for custom_field_value_change, see the Review Webhook Events help article.

For what custom fields are and where they appear, see Understand Custom Fields.

To create and edit them, see Configure Custom Fields.

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