Super League clubs Bradford and Wigan will be investigated by the RFL's independent judiciary panel for alleged breaches of the salary cap in 2005.
Clubs are permitted to spend no more than 50% of their income on players' wages, up to a maximum of £1.8m a year.
Meanwhile, Castleford, Hull, St Helens and Wakefield have been found guilty of minor breaches of the code.
Castleford and Wakefield were cautioned while Hull and St Helens were fined £5,000, some which has been suspended.
The judiciary panel will hear Wigan's case on Monday 7 August, while Bradford's will be stage at a later date.
In addition to the £1.8m maximum player wage cap, clubs are also bound by the "20/20 rule" whereby they can only have a maximum of 20 players earning in excess of £20,000 a year.
Punishments can range from a fine to a deduction of six points depending on the size of the breach.
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