Waterford FC owner Andrew Pilley has been sentenced to 13 years in prison.
Pilley, who also owns English League One side Fleetwood Town, was found guilty of two counts of running a business with the intention of defrauding creditors, one count of false representation and one count of being concerned with the retention of criminal property.
He was convicted at Preston Crown Court in May ahead of sentencing today.
The fraud relates to the mis-selling of energy supply contracts to small businesses and is not related to his football interests.
The 52-year-old had been remanded in custody before today's sentence.
Waterford FC said in a statement: "Waterford Football Club acknowledges the sentencing in the court case involving owner Andy Pilley.
"The club would like to reiterate convictions are against individuals and not Waterford FC, or any of the businesses associated with them, and will continue to operate as normal.
"The club will make no further comment at this time."
Details of the offences were revealed by British National Trading Standards.
At the heart of the fraud "was a web of interconnected companies that misled innocent small businesses across the UK" into signing long-term energy contracts between 2014 and 2016.
The fraudulent mis-selling included false or misleading statements about the length and price of the contract as well as competitor rates.
Charities including guest houses, children's charities and companies providing support services for disabled people were among those targeted.
Annual turnover at two principal companies grew from £15m to £75m between 2010 and 2015.
Turnover was over £100m by 2019. Combined profits were between £2m and £12m.
Three other individuals were also convicted.
Michael Bichard, chairman of National Trading Standards, said: "Small business owners were deliberately deceived and locked in to contracts that were long-term and expensive, leaving many businesses struggling to pay the bills and sadly driving some business owners into making the difficult decision to cease trading.
"This is not a victimless crime - small business owners have lost vast sums of money to this fraud and many businesses have gone under."
The Blues look set to finish second in the First Division and have added to their squad despite concerns for their future, including two new players today.
