[Below briefly focus on Sample Application format for Duplicate Birth Certificate Letter. You can follow these sample application to ask for a duplicate birth certificate as you have either lost the original one or you need to send documents and they need a sealed official copy. You can modify these sample as your requirement.]
Date…
Authority Name/Job Designation…
Commissioner/District/Certificate office…
Office Address…
Sub: Application for Duplicate Birth Certificate
Dear certificate office,
I am writing to you because I would like to request to have a copy of my birth certificate. My name is (Your Name) and I am (Age) old. When I was a kid my mum and dad got a divorce and I stayed with my mum. (Explain the actual problem and situation). I am applying for my first passport however I need my birth certificate but my dad took all the original documents and when I got back into contact with him after so many years he looked all over for it and couldn’t find it. (Describe in your own words).
So for this purpose, I need a duplicate of my birth certificate so that I can send it to the passport office and they have all the proof they need. (Explain on requirement). I hope that you can help me with this matter and as soon as possible. Many thanks and I look forward to hearing from you.
Yours sincerely,
Your Name…
Address…
Contact information and signature…