My parents filed their 2014 return as MFJ and applied their refund to the 2015 taxes and they also jointly sent a form 4868 extension form for 2015 with a check for expected taxes. They have until 10/15/2019 to file their 2015 tax return because of the extension. I am helping with their taxes and they want to file as MFS. My question is, do they split the applied refund and tax paid with the extension evenly between the two returns or is all of taxes paid for 2015 reported on one return?
