Download the application for Birth Certificate from 
   http://www.rgd.gov.lk/download_file/application_for_birth_certificate_b63.pdf

Fill the form and send it to the below mentioned address.

Fee for certified copies of Birth Certificates are ,

(i) If the registered number and the date of Birth  is known - 25 SL Rupees per each copy

(ii) If don't know the registered number, but the date of Birth is known, for 3 month search of registry - 50 SL Rupees per each copy

(iii) if you know only the year of birth, for 2 year search of registry, 100 SL Rupees per each copy

* You may pay the fee for a copy of the certificate together with the returning stamp fee in favor of the Registrar General by an international money order .

Address :
            Assistant Registrar General
            Central Record Room
            Maligawatta
            Colombo 10
            Sri Lanka