sorry for your loss. the tax basis would be the value on the date of death. really don't know the length of time between that occurrence and the sale. if the interval is relatively short and you sold at fair value, I would use the gross sales price as the date of death value. there could be an issue because the sale was between you as executor and your cousin (what the IRS would call a related party sale) but only if the IRS challenges the value.
as part of filing the 1041, since the money was distributed, a k-1 would go to each beneficiary reporting their share of the gain or loss so taxes if any on the sale is their responsibility.
