Decline after yes
Copy, fill the brackets, send from your own mail. Nothing here leaves this device.
Hi [Recruiter / HR name], Thank you again for the offer for [role] at [company]. After thinking it through with my family, I need to withdraw my acceptance. My decision is made — I will not be joining. I am sorry for the disruption. Please treat this mail as my formal decline. I appreciate the time you spent, and I wish the team well.
Templates, not legal advice. Match them to your appointment letter before you send.