I am working as a trainee in an audit firm. The purpose of an audit is to check the financial statements prepared by companies and report whether they present a true and fair view. In order to achieve this purpose we have to check the financial records from which the financial statements have been prepared and also the accounting process and calculations carried out by companies. These companies are involved in activities such as obtaining interest-based loans, having insurance and paying tax. Such activities exist in all kinds of companies even if their business itself is halal e.g. manufacturing companies. This means that we are obliged to check the accounting for interest, insurance and tax, without which we cannot give our report. My question is, is it lawful to perform audit?
In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātu
The work of an auditor to check financial statements and merely report on that is permissible. The auditor is not directly involved in the interest bearings transactions in anyway. (1)
And Allah Ta’āla Knows Best
Checked and Approved by,
Mufti Ebrahim Desai.
هذا إنما يقع على من واطأ صاحب الربا عليه فأما من كتبه أو شهد القصة ليشهد بها 
على ما هي عليه ليعمل فيها بالحق فهذا جميل القصد لا يدخل في الوعيد المذكور وإنما
يدخل فيه من أعان صاحب الربا بكتابته وشهادته
(Fath al-Bari (Ibn Hajr), Vol.4, Pg.394 , Qadeemi)(Contemporary Fatawa (Mufti Taqi Usmani), Pg.160, Idara-e-Islamiyat)