It is the largest tax robbery in German history — and at the same time one of the least understood. Between 2001 and 2012, banks, lawyers and hedge funds skimmed an estimated 36 billion euros from the German state. Not through classic tax evasion, but through a trick that let a single capital-gains tax payment be refunded multiple times — on shares “sold” to several buyers at the same time. This is the Cum-Ex scandal. Its smaller, less-famous brother Cum-Cum was even larger by volume. In 2026 cases are still pending in German courts — and politicians are still wrestling with the consequences. Here is the complete guide to Germany’s biggest tax scandal, what it means for investors today, and why the U.S. has its own equivalent under Section 1058.

1. Cum-Ex in one minute

Cum-Ex (“with-without”) is a tax trick built around the dividend record date. The name comes from Latin: a share is bought cum (with) dividend entitlement and sold a moment later ex (without) — the swap happens around the dividend payout. That sounds harmless. It becomes criminal as soon as three or more parties shuffle the same shares between each other and end up issuing two or more tax certificates for the very same tax payment.

The German tax office only ever sees one share and one withholding tax payment — but it refunds the tax to Bank A and Bank B and Bank C, because each bank can produce a credible certificate. Out of 25 percent withholding tax (Kapitalertragsteuer) on a €1 dividend, you get 50 or 75 cents in refunds. The state pays out more than it ever collected. The participants split the difference.

The scandal broke in 2017 with an international research consortium (“CumEx Files”), the first convictions came in 2018, and Germany’s Federal Court of Justice (BGH) finally classified the entire model as criminal in 2021. Even so, in 2026 the legal cleanup is still in full swing — against the main actors as well as the bank executives who let it happen.

2. The mechanism — how 36 billion was stolen

To understand how this worked, you need three building blocks: withholding tax, short selling, and the tax certificate.

Step 1 — withholding tax (Kapitalertragsteuer). When a German DAX company pays a dividend, it withholds 25 percent (plus solidarity surcharge) and remits it directly to the tax office. The domestic shareholder receives the net dividend plus a tax certificate that lets them apply for a credit or refund on their own tax return.

Step 2 — short selling around the record date. Here creativity enters. Investor A holds 100,000 Volkswagen shares just before the AGM. Investor B (or a hedge fund) sells “short” — shares it does not yet own — to Investor C, with delivery shortly after the dividend. Until the record date B holds nothing, but it can deliver later by borrowing or buying back the shares.

Step 3 — the duplicate certificate. Here is the twist. Both A and C believe they held the share over the record date. Both receive a tax certificate from their bank — even though the withholding tax flowed only once from the issuer to the tax office. With three or four nested investor circles, the refund is doubled or tripled.

Scaled to a Volkswagen AGM with €1 billion in dividend payments and 30 percent of the volume routed through Cum-Ex, that is €75 million per company per year. Across 30 DAX companies and 12 years, the totals quickly run into double-digit billions. Former finance minister Wolfgang Schäuble first put the damage at €5.3 billion in 2017, the renowned Mannheim Research Institute revised the figure in 2020 to at least €12 billion for Germany alone. Including Cum-Cum and similar models, the estimate widens to over €36 billion. Some prosecutors, notably Cologne Senior Prosecutor Anne Brorhilker, talk of “well over €30 billion” purely from withholding tax double refunds.

3. Main actors — the banks involved

Cum-Ex was not an isolated case but an industrialized business model. At least ten of the largest German and international banks actively participated for more than a decade. The most important players:

Maple Bank, a small Canadian-German subsidiary, went insolvent in 2016 solely because of Cum-Ex. After the German finance ministry demanded €450 million back, the bank’s equity could not cover it — even the banking license was revoked. Maple Bank is the first and so far only bank collapse triggered directly by the scandal, and it now serves as a warning that this business was existentially dangerous.

M.M. Warburg deserves its own paragraph: the Hamburg-based private bank was convicted in 2020 over €280 million in tax damages. The twist: Hamburg’s then-mayor, Olaf Scholz, met three times in 2016 with bank chief Christian Olearius — and Hamburg failed to demand repayment of the disputed taxes (which therefore almost lapsed). The case has occupied Hamburg’s parliamentary inquiry for years and continues to shape the political debate around the scandal.

4. Anne Brorhilker and Hanno Berger — the actors on both sides

No scandal works without people. On the prosecution side stands Anne Brorhilker, senior prosecutor in Cologne and head of the Cum-Ex unit. Since 2013 she has investigated more than 1,700 suspects, led hundreds of raids, and earned a reputation as an incorruptible enforcer. In 2024 she resigned in protest, saying she had been politically obstructed — the state government refused to give her enough staff, and she felt the cleanup was being sabotaged. Her move to the citizens’ initiative “Finanzwende” in May 2024 was a political earthquake.

On the perpetrator side stands Hanno Berger, a Frankfurt tax lawyer who industrialized Cum-Ex. Berger worked for the Hesse tax administration until 2009 and then jumped to the other side, advising the banks and hedge funds that systematically rolled out the model. A great deal of the documented Cum-Ex playbook traces back to his training sessions and engagements. He fled to Switzerland in 2012, was extradited in 2021, and in 2022 sentenced by the Wiesbaden regional court to 10 years in prison — the highest Cum-Ex sentence so far. A second conviction in Bonn added 8 more years in 2023, running concurrently. Berger is now incarcerated at JVA Frankfurt-Preungesheim.

Many other actors have been convicted alongside them: ex-HVB banker Martin Shields (suspended sentence as state’s witness), Nicholas Diable (suspended sentence as state’s witness), Christian Olearius (case suspended for serious illness), and over 30 other lawyers and bankers. The total number of convictions stood at more than 80 at the start of 2026, many of them suspended sentences thanks to plea deals or testimony.

5. Cum-Cum — the bigger but less-known sibling

While Cum-Ex dominates the headlines, the sibling business Cum-Cum was actually significantly larger. Estimates by the Mannheim study (2020): Cum-Cum cost the German state about €24.6 billion between 2000 and 2018 — almost twice as much as Cum-Ex (€12 billion).

The mechanism is more subtle. In Cum-Cum, foreign shareholders temporarily swap their shares with a domestic German party shortly before the dividend record date. Background: foreign shareholders cannot fully reclaim withholding tax, but domestic taxpayers can (or banks, with their own trading-book privilege, never had to pay it in the first place). The domestic party gets the full refund, returns the share after the dividend, and shares the surplus (typically 50/50) with the foreign owner.

The model looks more legal than Cum-Ex on the surface — formally, shares are simply lent — but materially it bends the same tax logic. The Federal Tax Court (BFH) in 2018 branded it “abusive”, which is functionally tax avoidance. Since 2016, German tax law (§ 36a EStG) requires a 45-day minimum holding period around the dividend record date, which made Cum-Cum effectively unprofitable. But the past lingers. HVB alone repaid more than €100 million in Cum-Cum claims; in 2026, parallel claims continue against Deutsche Bank, Commerzbank, and many others.

6. How the scandal was uncovered

Cum-Ex might still be undetected today without a chain of whistleblowers and investigative journalists. The key figures:

• Eckart Seith, a Stuttgart lawyer, was among the first in 2011 to recognize the systemic character of the trick and persuaded a client (a private bank) to file a voluntary self-disclosure.
• Anonymous insiders from Sarasin Bank started supplying documents to the Swiss federal prosecutor in 2015 — the first hard evidence of criminal intent at the banks.
• The CORRECTIV team (Berlin) and the international consortium CumEx Files: 19 outlets in 12 countries, including ARD, ZDF, Le Monde and La Repubblica. Their first big release in October 2018 showed that France, Belgium, Denmark, Italy, and Norway were also affected — combined damage Europe-wide above €150 billion.
• Anne Brorhilker built her specialist Cologne unit from 2013 onward and ordered raid after raid. Her work led to the first plea-deal testimonies (Shields, Diable) and to the first convictions in 2018.

In May 2014, Spiegel magazine published the first comprehensive coverage. The banks’ response: minimization. The trick was “common practice,” “politically tolerated,” a “grey zone.” Only the BGH in 2021 settled the matter for good: Cum-Ex was, and always had been, tax evasion — not loophole exploitation.

7. Status 2026 — cases, convictions, open claims

After more than twelve years of legal cleanup, here is the picture in 2026:

• Convicted participants: over 80, with around half receiving custodial sentences. Highest sentence: 10 years (Berger).
• Active proceedings: roughly 1,700 suspects, 130 ongoing criminal cases at prosecutors’ offices in Cologne, Frankfurt, Munich, and Hamburg.
• Recovered taxes: approximately €5.8 billion confirmed reclaimable (Q1 2026). Of that, ~€3.2 billion has actually been collected. The rest risks being lost to statute of limitations.
• Political review: Hamburg’s Cum-Ex inquiry committee and the Bundestag’s finance committee continue working. The German chancellor remains under pressure for the Olearius meetings.
• Statute-of-limitations problem: Tax claims from 2007–2010 partially expired on 31 December 2024. The federal government extended the statute for severe tax evasion from 10 to 15 years in early 2025 — but too late for many cases.

Most important new ruling in 2025: in July, the BGH upheld the Maple Bank judgment against the former CEO. That is the final appellate stage — Maple Bank is now the textbook Cum-Ex case.

8. Implications for retail investors

Are retail investors Cum-Ex victims? Not directly — as a shareholder you receive your dividend with the standard 25 percent withholding tax deducted. Indirectly, however, you are heavily affected: every German taxpayer carries roughly €400 of damage. And the regulatory response has changed your investing life.

Practical tip: if you sell a German share around the dividend record date and buy new shares, watch the 45-day rule — otherwise you do not collect the withholding tax in full. Plus: keep tax certificates for 10 years, because Cum-Ex has shown how vital documentation is in disputes.

9. International — the U.S. and its own Cum-Ex (Section 1058)

Cum-Ex is not just a German phenomenon. The CumEx Files investigation showed that at least eleven European countries were affected, with combined damages above €150 billion. France lost about €33 billion, Italy €22 billion, Denmark €12 billion (the Danish tax authority Skat was one of the largest single victims). Belgium, Switzerland, Austria, and the Netherlands each have their own ongoing cases.

The U.S. has a similar construct — known as “Section 1058 securities lending”. Hedge funds use U.S. stock lending: they borrow shares shortly before the dividend record date, receive a “substitute payment” instead of the dividend (tax-treated differently), and thereby avoid the 30 percent U.S. withholding tax for foreign investors. Since 2016, the SEC and IRS have taken action against “dividend arbitrage” in several cases, with cumulative penalties over $800 million. But unlike German Cum-Ex, the U.S. model is largely legal in form — the “trick” lies in the contract type, not in a multiple refund. It costs the U.S. Treasury an estimated $1 to $4 billion per year.

The UK and Australia have similar systems. The OECD attempted in 2023 the first cross-country estimate: worldwide $200–400 billion per decade in tax revenue lost to dividend-driven schemes. The reform conversation in 2026 centers on the EU’s “FASTER” directive, which from 2030 plans a unified withholding-tax regime with real-time reconciliation.

10. Timeline — from the 1990s to today

11. FAQ — most-asked questions

Bottom line

Cum-Ex and Cum-Cum are the largest tax robbery in German history — €36 billion, executed by banks, lawyers, and hedge funds, with a dirty choreography of short sales and tax certificates. The scandal is still in legal cleanup in 2026, with Hanno Berger as the highest-sentenced perpetrator and Anne Brorhilker as the symbolic figure of the slow victory.

For retail investors, the central lesson is not “beware of Cum-Ex” (it is practically impossible today), but beware of seemingly harmless tax structures that look too good to be true. If an adviser sells you a strategy that “the state simply does not know about”, assume that either you or the adviser will end up in court. German tax law is many things, but rarely permanently naive.

The 45-day minimum holding period around dividend record dates is the most important consequence for your tax life. If you buy shares shortly before a dividend and sell shortly after, double-check whether you fully recover the withholding tax — otherwise the dividend yield will be up to 25 percent lower than you assumed. That is the Cum-Ex legacy, sitting right inside your tax return.

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