certain doubt - submission of documents

SIR, I am an advocate, doing practice in taxation. Now I need a clarification/advice that whenever I take a certain task/assignment like Audit or assessment of companies, including Government companies which are related to respective statutory authorities, I am given duly authorization under specified forms ( as per the rules framed under that respective rules) by such companies. Whenever, I am in need of submitting certain accounts/documents/records/statements to the concerned authorities, do I have to submit them under my letter head or even submitting such accounts/documents/records/statements under the respective company letter head only but with my sign,  which is the correct method as to (i) submitting such documents to statutory authorities under my letter head with my signature or (ii) submitting such documents to statutory authorities under the respective company letterhead with my signature. Kindly advise sir.