The Addicks finished the season on a high with a 4-2 victory over Norwich, who will join them in League One following the defeat, but Parkinson insists there will be no summer rest despite not knowing whether or not he will be in charge come August.
"We've put together a pre-season but I can't stress enough that the next six to eight weeks will make or break next season," he told the club's official website.
"The season doesn't start in August, it starts now. You can be the best coach in the world but it's all about recruiting the players and that has got to start straight away.
"The name of Charlton, The Valley and the training ground won't get us promoted next year. What it will do is enable to attract good players and the recruitment of those players has got to be absolutely spot on as we go into the summer.
"We're always scouting players and over the last three months we've been
here, there and everywhere. We've given the board a list of players who we feel we can attract. People think managers go away and spend the summer on the beach; they don't - the hardest part of a manager's job is now."