@gjfudge wrote:
Do I need to submit any proof of my basis and if so, how?
You do not have to submit proof of your basis, but you might need such proof should the transaction ever be questioned by the iRS.
So that it is clear, your basis is almost certainly the fair market value on the date of death of your father in 2004.
If the property was appraised shortly after that date by a certified appraiser, that value is most likely sufficient for your purposes.
However, if the property had appreciated between 2004 and 2022, when you sold the property to your son for $115,000 (which seems likely), then the transaction would actually be part gift/part sale. The end result would not change for you, personally, other than you could be required to file a gift tax return (Form 709), but you son's basis could vary.
