> For the complete documentation index, see [llms.txt](https://docs.truecaller.com/truecaller-for-business/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.truecaller.com/truecaller-for-business/features/call-reason/what-is-the-prerequisite-to-start-a-call-reason.md).

# What is the prerequisite to start a Call Reason?

The number for which Call Reason is to be displayed must be a valid phone number and already a Verified business or Priority number with Truecaller.


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