George K. Baum & Company v. Twin City Fire Insurance Co., 760 F.3d 795

Baum (Missouri corp.) bought a professional services/errors-&-omissions policy from Twin City, issued to Baum’s New York office to avoid Missouri surplus-lines tax; policy included a New York-specific endorsement.
In Aug–Sept 2003 Baum notified Twin City of an IRS investigation into municipal-bond underwriting; Twin City treated that IRS inquiry as a claim and Baum later settled with the IRS.
In 2008–2010 multiple municipal lawsuits (the "derivatives litigation") were filed alleging related wrongful acts; Baum notified Twin City of those lawsuits in April 2010 (years after policy expiration in 2004).
Twin City initially denied coverage as untimely (claim not made during policy period), later conceded the IRS matter and derivatives litigation were related but asserted denial for untimely notice of the later lawsuits.
The district court applied Missouri law, held insurer must show prejudice from late notice, found Twin City conceded no prejudice, and ruled Twin City liable but that a $3 million self-insured retention (not $1M) applied to the derivatives litigation.
On appeal the Eighth Circuit held New York law governs but affirmed coverage because the policy is ambiguous regarding notice for later suits that arise from a timely, earlier-notified claim; the $3M retention also applies.

Issue	Baum's Argument	Twin City’s Argument	Held
Choice of law	Policy should be governed by Missouri law (insured’s principal place)	New York law governs because policy was issued to Baum’s NY office and contains NY-specific endorsements	New York law governs under Restatement §187 principles
Timeliness of notice / coverage	Baum gave timely notice of the underlying IRS claim in 2003; later lawsuits are "a single CLAIM" deemed made in 2003, so coverage applies	Policy requires notice of each later lawsuit within 60 days after policy expiration; Baum’s 2010 notice was untimely and bars coverage under NY law	Policy ambiguous on notice for subsequently-filed suits tied to a timely-notified claim; ambiguities construed against insurer → coverage affirmed
Waiver / estoppel of late-notice defense	Twin City waived untimely-notice defense by not raising it in its initial denial	Twin City argued later it preserved rights and raised untimely-notice defense timely in litigation	Court finds waiver/forfeiture issues immaterial because policy ambiguity resolves coverage in insured’s favor
Applicable retention amount	$1M retention for standard claims	$3M self-insured retention applies to claims "relating to" underwriter/seller municipal-bond activity	$3M retention applies because derivatives litigation relates to Baum’s underwriting/selling activities

Salve Regina Coll. v. Russell, 499 U.S. 225 (federal diversity/choice-of-law principle)
Klaxon Co. v. Stentor Elec. Mfg. Co., 313 U.S. 487 (forum state choice-of-law rule)
Viacom, Inc. v. Transit Cas. Co., 138 S.W.3d 723 (Mo. 2004) (Missouri adoption of Restatement §§188/193 for casualty insurance)
Dean v. Tower Ins. Co. of N.Y., 979 N.E.2d 1143 (N.Y. 2012) (insurance-contract ambiguities construed against insurer)
Briggs Ave. LLC v. Ins. Corp. of Hannover, 899 N.E.2d 947 (N.Y. 2008) (New York no-prejudice rule context)