He works as an accountant and does not pray in congregation occasionally because of that

Praise be to Allah.

Prayer in congregation is obligatory for men who are able to do it, according to the more correct of the two scholarly opinions, based on a great deal of evidence that has been explained in the answer to question no. 8918. 

An exception from that is made for the one whose work cannot be left because obvious harm would result from that, such as those who guard important places or doctors doing surgery and the like; they may stay away from prayer in congregation. 

As for working as an accountant, there does not seem to be any reason for not praying in congregation because of it, because you can close the books, computers and offices in order to go and pray. The boss has no right to stop employees from praying in congregation. This has been discussed in the answer to question no. 72895. 

We advise you to try to pray in congregation and to do things that will help you to do that, and to advise your bosses at work, because prayer is the most important pillar of Islam after the Shahaadatayn, and it is the cause of success and prosperity in this world and in the Hereafter. 

And Allaah knows best.