---
title: "Why didn't the sibling discount apply?"
description: "The rule picks the younger children by date of birth at billing time. A missing DOB, separate families, or a date window are the usual causes."
type: troubleshoot
updated: 2026-08-26
canonical_url: https://help.nestlicare.com/owners/faq/why-didnt-the-sibling-discount-apply
roles: ["super_admin", "center_admin"]
platforms: [web]
---
The sibling discount is worked out **at billing time, by the children's ages**. NestliCare orders a family's children by date of birth and applies the rule to the younger ones. You never tag a child as "the second child".

So when it does not apply, check:

1. **Are the children in the same family?** Siblings split across two family cards look like two only children.
2. **Do both children have a date of birth?** A missing DOB can make a family look like it has one child. Fill it in on the child's profile.
3. **Does the discount's date window overlap the invoice's billing period?** A rule with an end date stops firing once no part of a period overlaps it.
4. **Was the discount active before the invoice was generated?** Discounts apply at generation time. A rule you added today reaches the next invoice, never existing ones.

Fix the cause, then void the wrong invoice and create a corrected one; existing invoices keep their original figures.

Related: [Subsidies and discounts](/owners/billing/subsidies-and-discounts), [Credits and referral bonuses](/owners/billing/family-credits).