For 2016 tax year, I wrote my client an email in April 2017 that said his extension form 4868 was in our shared dropbox folder. I said all he had to do was write in the amount he wished to pay and mail it by the deadline with a check. This is how he asked me to do it for both 2014 and 2015 tax years because he wanted to make a last minute decision on how much to pay.
The client responded to my email, so I know he saw it, but didn't give a clear confirmation that he would mail it. I efiled the return in Sept and very quickly he got a failure to file penalty of $7k based on unpaid balance of $30k. Unfortunately for him he has had penalties every single year dating back to at least 2011 so the first time penalty abatement is off the table.
I have had conversations with him about all sorts of reasons why he might be able to claim reasonable cause but there is nothing there. It's simply a case of him not mailing in the extension because as he told me later, he thought I was efiling it. I know relying on bad advice from the IRS or a CPA can be used, but should I advise my client to use miscommunication as an attempt at reasonable cause? $7k is a lot of money, but somehow I feel I'm throwing myself under the bus advising him to do this.