Hi @kaushal_snow,
That is a default functionality from SC Catalog Item widget:
https://docs.servicenow.com/bundle/tokyo-servicenow-platform/page/build/service-portal/concept/sc-ca...
That information will always show whenever you have mandatory fields in your catalog item. Check the Show field validation messages in the documentation link.
You can use this widget in your portal since its OOB from ServiceNow.
If you found my answer helpful or correct in any way, please don't forget to mark it to help future readers! 👍
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Kind regards,
Marcos Kassak
Solution Consultant 🎯
