If you are confirmed with the date of death as 21st May 2021 you can calculate his salary up to 20th May 2021 and the additional benefits, you may give in his final settlement. Please do not leave any room for any query from the EPFO.
There are cases where the workman had performed his duty and died after reaching home safely. In such cases, the salary calculation should be up to his last working day.
Suresh