Castleford has claimed that staging three home games in the Super 8s last season has cost the club around £100,000.
Attendances at the Jungle were down for the Tigers for their Super 8s fixtures with St Helens, Warrington and Hull FC compared to their regular season match-ups.
Castleford CEO Steve Gill said the club needs to find out why crowds had dropped.
“It is a substantial loss for a club like ourselves and we aren’t exactly sure why it happened,” Gill told The Yorkshire Evening Post.
“Two of the games were on Thursday nights, not Sundays, while it may also have been to do with the summer holidays and people being away, but we’re really not certain.
“We will be working really hard to sort it out for next season.
“Obviously, we don’t know when those Super 8s fixtures will be yet but we have to make sure we get our attendances up.”
The Super 8s concept was introduced in 2016 and will continue this season.
Gill said Castleford had a combined drop of about 5,000 fans for the three games.
“Maybe sometimes people think we’re in the top eight and so can relax a little,” he said.
“But they probably don’t realise the Super 8s are a continuation of our regular season.
“The Super 8s is a great concept and we did back it from the start so we’re not going to moan about it now.
“But we do need to make that shortfall up somewhere down the line and must ensure our attendances in the Super 8s next season do compare to those regular round fixtures.
“I think there’s a few tweaks and things needed to be done but we should be able to build the format up even more in 2016.”