Why the reported returns are the fraud, and not merely wrong. An incompetent manager loses money and reports the loss. A Ponzi operator has no loss to report because there are no positions, so the statement is composed rather than computed. That has a counterintuitive consequence for how these schemes are spotted. A fabricated return has no reason to fluctuate, so the performance record is frequently smooth, modestly attractive, and remarkably consistent through market conditions that hurt everyone else. Consistency is the signature, not the comfort. A strategy that genuinely earns a return in markets must be exposed to something, and something that is exposed moves.
The arithmetic is what makes collapse certain rather than likely. Every dollar promised to an existing investor is a dollar that must be found from a new one, and the promised amounts compound. The scheme therefore requires contributions to grow at least as fast as the promised returns on an ever larger base, indefinitely. Nothing grows at a compounding rate indefinitely, so the end is arithmetic rather than bad luck. The usual proximate trigger is a wave of redemption requests, which is why market stress ends more of these than investigations do.
The structural defense is separation, and it is the one that actually works. If the person recommending an investment is also the person holding the assets and also the person producing the statements, then the statements can say anything. If the assets sit at an independent custodian that reports directly to the investor, the operator has to reconcile with a record they do not control. This is why an investor can perform a useful check without understanding the strategy at all: confirm that the account is held at a recognizable custodian, confirm the statements come from that custodian rather than only from the adviser, and check the balance through the custodian's own channel. The Securities and Exchange Commission's custody rule addresses this problem for registered investment advisers, and that rule has its own entry here.
Practical tells, none of them conclusive on its own. Returns that are high and unusually steady. A strategy that cannot be explained, or that is explained as proprietary. Difficulty getting money out, or pressure to reinvest rather than withdraw. Statements produced by the adviser rather than by a third party. An auditor that is tiny, unknown, or related to the operator. Recruitment through a shared community, a congregation or a professional association, which is a distinct pattern with its own name. And registration that cannot be confirmed: an adviser's registration can be checked at adviserinfo.sec.gov and a broker's at FINRA's BrokerCheck, and an entity that appears in neither is a fact worth knowing before anything else.
A Ponzi scheme is not a pyramid scheme, though the two are often conflated. In a pyramid scheme the participants know they are recruiting, and the returns are openly tied to bringing in more people. In a Ponzi scheme the investors believe they have bought into a strategy and generally have no idea where the money paid to them came from. The legal treatment and the tax treatment differ accordingly.
The tax aftermath is real relief and it is widely missed. A loss from a Ponzi scheme is a theft loss arising from a transaction entered into for profit. Revenue Ruling 2009-9 holds that such a loss is deductible under section 165(c)(2) rather than as a personal casualty or theft loss under 165(c)(3), which matters a great deal: the limitation that restricts personal casualty and theft losses to federally or state declared disasters reaches 165(c)(3) losses, not these, and the ruling also confirms the deduction is not treated as a miscellaneous itemized deduction and can generate a net operating loss. Revenue Procedure 2009-20, as modified by Revenue Procedure 2011-58, then offers an optional safe harbor: an investor who follows its procedures gets certainty on the year the theft is treated as discovered and on the amount, deducting 95 percent of the qualified investment if they are not pursuing third-party recovery, or 75 percent if they are, reduced by any actual recovery and any potential insurance or Securities Investor Protection Corporation recovery. The safe harbor requires the arrangement to have reached a defined legal stage, generally an indictment, information or criminal complaint against the lead figure, which is why it is not available the moment an investor suspects something. The 2011 modification added a third route for the case that had been shutting investors out through no fault of their own: where the lead figure has died, so that no criminal charge is possible, a civil complaint or similar enforcement filing by a state or federal authority alleging substantially the elements of the scheme will serve instead, provided a receiver or trustee was appointed or the assets were frozen.