AM Best Drops Prime Insurance to B as Reserve Charges Accelerate Past $218 Million

Prime Insurance Company's carried loss reserves grew from roughly $358 million at year-end 2023 to about $483 million at year-end 2024 while the company was strengthening them, and the strengthening then sped up: $111 million in 2024, $29 million in 2025 and $78 million in the first six months of 2026 (AM Best, August 28, 2026). AM Best's two-notch cut to B (Fair) from A- (Excellent) prices that acceleration.

Under review with negative implications is where the rating stays until Prime files its third-quarter 2026 statutory statements and meets AM Best on reserves, risk-adjusted capital and mitigation. Prime's June 30 carried balance is the third consecutive reserve figure the agency has declined to treat as a floor.

Key Takeaways

• $218 million of cumulative adverse development landed across thirty months, January 2024 through June 2026, at a carrier whose surplus sits in AM Best's Financial Size Category VIII, the $100 million to $250 million band.
• $358 million and $483 million are the year-end 2023 and 2024 reserve bases implied by the release's own percentages, which means the book grew 35% in a year while its prior years were being re-picked upward.
• $21 million of the 2025 charge arrived in the fourth quarter: the January release carried $8 million through nine months and the August release carries $29 million for the year, so most of it landed in the quarter whose balance the year-end actuarial opinion covers.
• 31% of prior reserves in one year is roughly four times the 8.0% one-year adverse development Milliman measured across the industry's commercial auto liability book for 2024.
• $57.9 million is what minority owner and quota-share reinsurer RLI carried the Prime stake at on June 30, 2026, up from $53.5 million at year-end, across the same six months in which Prime booked $78 million of statutory strengthening.

Three Charges and the Reserve Base Underneath Them

AM Best states each charge two ways, as dollars and as a share of prior year-end reserves, and the pair lets a reader back out what Prime was carrying. $111 million at 31% puts year-end 2023 reserves near $358 million; $29 million at 6% puts year-end 2024 near $483 million (AM Best, January 29, 2026, and the August release). No percentage accompanies the 2026 figure, so the $78 million can only be set against the last derivable base, where it equals about 16% in six months.

Timing carries more information than size. AM Best's January release measured 2025 at $8 million through nine months and flagged the potential for more at year-end. Year-end came in at $29 million, so $21 million landed in the fourth quarter, the quarter whose carried balance the Statement of Actuarial Opinion covers. Six months later the company added $78 million, more than the whole of 2025 and 70% of the 2024 charge that had already cost 40 loss ratio points.

A one-time true-up runs the other way. A carrier that re-picks its tail once takes the large charge, then the following periods show small residual movements as the new selections prove out. Prime's residual movements grew. That is the signature of selections that were moved toward the emerging experience but not all the way to it, so each subsequent diagonal of the triangle exceeded the pick again.

Why an E&S Commercial Auto Book Keeps Developing

AM Best's January release names commercial auto liability as Prime's largest line and describes the business as an excess and surplus writer that grows through "aggressive pricing and manuscripted terms" (AM Best, January 29, 2026). The rated unit consolidates the admitted affiliate Prime Property and Casualty Insurance Inc., formed in Illinois in 2013 to write commercial auto in states that require it on an admitted basis, so both books' reserves sit inside the same 31%. Prime's rating disclosure lists Florida, New Jersey, Texas, California, Illinois, Pennsylvania and Louisiana as its primary markets, which is close to a roll call of the venues driving nuclear verdicts.

Industry commercial auto liability experience frames how far outside the norm Prime sits. Milliman's statutory analysis found 8.0% adverse one-year development on the line for 2024, with every accident year from 2016 forward moving adversely, and AM Best estimates the line as a whole is under-reserved by $4 billion to $5 billion. actuary.info has tracked the line's fourteenth consecutive underwriting loss and severity compounding near 8% a year. Against that, Prime's 31% is roughly four times the industry's bad year.

Premium arithmetic explains why the ratio runs so high. AM Best describes the $111 million 2024 charge as 40 loss ratio points, which puts the earned premium denominator near $278 million, while carrying reserves at $483 million by year-end 2024. Premium had already fallen from $227.8 million in 2022 to $185.6 million in 2023 (AM Best, February 5, 2025). A shrinking premium base under a growing reserve base raises reserve leverage by definition, and every dollar of strengthening then lands on a smaller surplus.

That is the transmission to capital. AM Best's rating disclosure for the August action states that "significant adverse reserve development has resulted in higher reserve leverage, declining statutory surplus and weaker regulatory risk-based capital levels" (AM Best rating disclosure, August 2026). Under the NAIC's RBC framework, a ratio below 300% of authorized control level capital brings the trend test into play, below 200% requires an action plan, and below 70% obliges the regulator to take control.

$218 million of charges against a surplus band that tops out at $250 million is why the agency revised enterprise risk management to marginal from appropriate and wrote that further development "has the potential to prompt regulatory actions via lower regulatory risk-based capital (RBC) levels." Its default study in the same disclosure puts the ten-year default rate observed for B-rated insurers at 8.81%, against 2.80% at A-, the level Prime held four weeks earlier.

What the Minority Owner's Books Show

RLI holds a minority stake in Prime Holdings Insurance Services and has assumed general liability, excess, commercial auto, property and professional liability from both Prime carriers under a quota share agreement (RLI Corp, 2025 Form 10-K). On the fourth-quarter 2025 call, CFO Aaron Diefenthaler said the quarter's net earnings reflected "Prime's core operating results based on our minority ownership and a reduction to Prime's value on our balance sheet to $53 million," and confirmed that "unconsolidated investees only includes our minority investment in Prime Holdings" (RLI Q4 2025 earnings call).

Two quarters later the carrying value had moved the other way. RLI's second-quarter 2026 Form 10-Q carries the investment at $57.9 million at June 30, 2026, up from $53.5 million at December 31, 2025, and records $5.1 million of equity in earnings of unconsolidated investees for the half. Those are the six months in which the operating companies booked $78 million of statutory adverse development. Neither document reconciles the two; Prime Holdings also owns a brokerage and a claims-handling unit, GAAP and statutory reserving differ, and the equity pickup can trail the statutory quarter. Even so, the divergence is the widest the two series have shown.

RLI's sharper exposure is the treaty. A quota share takes a fixed share of ceded premium and of the reserves behind it, so for the treaty years a slice of the same commercial auto liability that developed $78 million adversely at Prime sits inside RLI's casualty segment, which reported $75 million of favorable prior-year development companywide in the same half. RLI has published no Prime-specific reserve figure.

AM Best's logic closes on itself. Each charge that makes Prime's reserve more adequate makes its surplus less so, and lower surplus is the RBC trigger the agency named. Prime cannot strengthen its way to a rating floor without spending the capital the floor is measured on, and the third-quarter statement AM Best is waiting for will show both sides of that trade at once.