Deductions & credits

 My father passed in Dec 2018 and  my  2 brothers and I  just completed probate in the state of Florida and the home was transferred to our names  in  as of Aug 27, 2019  ,  we just sold the home  Oct.11, 2019  . We are all Massachusetts residents.  Is there  a  formal document that is  required from a real estate agent for  the cost basis to establish  FMV,   I would say FMV did not change from the time it was transferred in our names in Aug 2019 compared to  when we sold it in Oct. 2019 . Question is how do I prove that and do I need to ?  Also the proceeds were all processed via my SS# on the 1099-S but if there is no tax liability I don't think this would matter would it ? As I see it there are no capital gains.    Finally  at the time of the sale there was a mortgage that was satisfied and moneys were left over that we split equally , this is not taxable in our state as I understand it  as there is no inheritance tax in MA.  is this correct, I just need to make sure before we split all the proceeds that I am not on the hook  for taxed related to this .