**Judicial estoppel** / **Collateral estoppel** (issue preclusion) / **Equitable estoppel**

 Here's how the three separate out:

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**Judicial estoppel** —

 bars a party from taking a position *inconsistent with one it successfully argued and won on* in an earlier proceeding.

• Why is it called that?

Judicial: 

 Relating to a [court] or [judge] (from the Latin judicium).

Estoppel: 

 A legal principle that [stops] or ["plugs"] someone from contradicting what they previously established as true (from the Old French estouper, meaning "to stop up" or "plug"). Purpose: 

  Protect the integrity of the courts, stop parties from "playing fast and loose." 

Elements: 

(1) clearly inconsistent later position, 

(2) the earlier position was *judicially adopted* (party actually succeeded on it), 

(3) unfair advantage if allowed. It doesn't require reliance by the other party — the "victim" is the court system itself. *New Hampshire v. Maine*, 532 U.S. 742 (2001).

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**Collateral estoppel (issue preclusion)** —

 Bars *relitigating an issue* that was actually litigated and necessarily decided in a prior case between the same parties (or their privies). 

  It's about the *issue*, not a party's position — and it applies whether or not the party "won." 

  Collateral estoppel, also known as "issue preclusion," is a legal rule that stops a party from arguing an issue of fact or law that a court already decided in a past case. 

• Elements generally: 

  Same issue, actually litigated, necessarily decided, final judgment, same parties/privity.

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**Equitable estoppel** —

 Bars a party from asserting a claim or right where its own conduct (a misrepresentation of fact) induced another party's *detrimental reliance*.

  This one is about protecting the reliant party, not the courts. Elements: 

• False representation, knowledge of the truth by the party estopped,

• Ignorance of the truth by the other party, intent that the other party act on it, and actual detrimental reliance. 

  Against the IRS specifically, equitable estoppel is rarely successful — courts require affirmative misconduct, not mere silence or an erroneous ruling.

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**The core distinctions:**

- Judicial estoppel =

 Protects the *court's integrity*, triggered by a party's own prior *success* on an inconsistent position.

- Collateral estoppel =

 Protects *finality of issues*, triggered by prior *litigation and decision* of that specific issue.

- Equitable estoppel =

 Protects a *party's reliance*, triggered by *misrepresentation + detrimental reliance*, no prior judgment needed at all.

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A quick tell for fact patterns: 

• No prior lawsuit involved

 → it's equitable estoppel or nothing. 

• Prior lawsuit, same issue decided

 → collateral estoppel.

• Prior lawsuit, party won by taking position X and now wants position Y 

→ judicial estoppel