On Tuesday, Uli Hoeness cheered his club from the stands as they progressed to the next round in the Champions League against Arsenal. on Thursday, the former Germany international and president of Bayern Munich sat in silence as a judge sentenced him to three and a half years in jail for tax fraud calculated to have cost the state more than €28.5m.

Hoeness, who won the World Cup with West Germany in 1974, last year admitted to squirrelling large profits made on the stock market into a Swiss bank account, opting for what German law calls "voluntary disclosure", where evaders can avoid trial by detailing taxes they have skipped and paying them back with 6% interest.But during this week's trial in Munich, it not only emerged that the sums Hoeness evaded were almost 10 times higher than previously assumed, but also that he failed to disclose his accounts within the rules.

Prosecutor Achim von Engel described the case as a "particularly grave case of tax evasion", calling for five and a half years in prison. The defence sought a suspended sentence and now has a week to appeal against the verdict.

Even before the sentencing, the most high-profile tax evasion trial in German history has already had a noticeable effect: more than 26,000 German tax evaders have opted for voluntary disclosure since the Hoeness revelations hit the headlines in 2013. In Bavaria alone, the figure has quadrupled since 2012.

Reactions varied from fans' laments to those decrying the sentence for leniency. The country's largest-selling tabloid, Bild, welcomed the verdict: "Bitter for Hoeness, good for tax justice", ran the headline. On Twitter, Daniel Mack, a Green politician, called the sentence "the longest sending-off in Bundesliga history".

Hoeness's defence lawyer, Hanns Feigen, had repeatedly drawn attention to the social causes to which the Bayern president had committed himself. Strong-willed and often disliked by other teams' fans, Hoeness also had a reputation for running Germany's most successful club with the genial atmosphere of a family business.

He arranged for his former strike partner Gerd Müller to be given a job at the club when the retired star was suffering from alcoholism, and organised support for another player, the talented midfielder Sebastian Deisler, who was blighted by bouts of depression. Repeatedly lauded for his charity work, Hoeness told Bild said in 2005: "I know it's stupid, but I pay all my taxes." The details that have emerged over the last 15 months paint a different picture. Between 2001 and 2010, he made more than 50,000 stockmarket transactions. A self-confessed luddite when it came to using computers, Hoeness conducted most of his deals via a hand-held pager, often during matches or boardroom meetings. Among Bayern colleagues, the gadget was jokingly known as Hoeness's "Tamagochi".

Asked in an interview with Die Zeit if he was addicted to gambling, Hoeness said: "I don't consider myself ill, if that's what you mean ... Maybe I was close to it for a couple of years. But nowadays I consider myself cured." His son Florian, 34, had interjected to point out that "the family begs to differ a little on this point".

With Barcelona having recently been charged for tax fraud over the signing of Brazilian star Neymar, two of Europe's most successful clubs are now under pressure to repair their reputation. Bayern say they won't comment on the sentence until after the appeal, though a statement on the future of the club's presidency from the supervisory board – which contains high-profile executives from Adidas, German Telekom, Volkswagen and Audi – is expected on Friday.

On Saturday, Bayern will play Bayer Leverkusen in the German league. If Hoeness attends, it is likely to be the last match he will watch in person for some time.