I met him and I described my judgement below

The 2018 and 2019 corporate tax returns were never filed.  He told me that the company was terminated in 2019 - illegally by one of the partners.  He told me that his six partners have not communicated with him or inquired about the status of the tax returns.  There are big losses that each of them possibly can deduct. I was surprised.  He said he knows that one partner has deducted his investment on his individual tax return.  He doesn't want to talk with them (as they have opposed him on certain business matters) and he thinks the ugliness of their separation and a lawsuit could arise  should they get K-1s from him.

I know this isn't right, but what would be the pros and cons of not listing those six as shareholders on the S Corporation tax return?  One thought would be to proportionately reduce the P&L so that my client doesn't receive more loss than he has a right to take.  

I don't think a taxpayer would know about a K-1 with a loss if they were not told or didn't review their transcripts. The IRS would not advise taxpayers, would they?

I'm going to file with all the partners, but I am finding that is an odd and interesting situation because. It something I have not ever dealt with.

@IRonMaN