Question Summary:
It is permissible for you to do the accounting on the returns in reference

Question Detail:

I work for an accounting firm where I mostly work on clients in industries such as real estate, consulting, sales etc. However, I was assigned a return for a store that derives most of its revenue from selling alcohol, is it permissible for me to work on this return?

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuhu
You are working for an accounting firm that assigned you accounting for their client. You are not responsible for the type of earning of the client. You are simply fulfilling your responsibility as an accounting employee to your accounting firm. It is permissible for you to do the accounting on the returns in reference.
 
And Allah Ta’āla Knows Best
Ismail Desai,
Darul Iftaa
 
Checked and Approved,
Mufti Ebrahim Desai.