First paragraph- This paragraph is the most important as here you clearly mention the type of statement with a little brief introduction to it. Also you mention your main reason for writing such a statement.
Second section-In this section you need to mention your full name (official) with your permanent address. You also mention the list of documents that you are enclosing to prove your above statements. By this letter you certify that all documents are without any discrepancy or inconsistency at all. Also in case of any such disagreement you may be contacted at the earliest.
Third paragraph-Here you sum up your statement to certify that you shall be liable to be taken to the court of law in case of ambiguity in your statement. You also do not hold your workplace/bank/university (depending on your statement) responsible for your misbehaviour.