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Uninsured motorist (UM) coverage pays you when another driver who hits you has no liability insurance, or leaves the scene (hit-and-run), up to your UM limit. Underinsured motorist (UIM) coverage can pay when the other driver has insurance, but not enough to cover your injury bill, up to your UIM limit. Both are for injuries (and sometimes property damage) to you and your passengers — not for damage you cause to someone else. Rules differ by state: some require UM or UIM, some require insurers to offer it with a signed rejection, and some (like Tennessee) put it on the policy by default unless you reject it in writing. Here are the facts, with sources and dates. We don't sell insurance or give quotes.
Checked October 15, 2026
Estimated uninsured in 2023 (Insurance Research Council via III; 2025 IRC study (2023 data)). Method: Ratio of uninsured motorist claim frequencies to bodily injury claim frequencies (III Facts + Statistics: Uninsured Motorists (IRC 2025 study; 2023 data; "20 states and D.C. have mandatory UM or UIM"))
5th-highest among states and D.C. in the 2023 IRC estimates published via III. Countrywide rose from 12.4% in 2017 to 15.4% in 2023 (III Facts + Statistics: Uninsured Motorists (IRC 2025 study; 2023 data; "20 states and D.C. have mandatory UM or UIM"))
III says have mandatory requirements for uninsured or underinsured motorist coverage. Our table below lists 21 jurisdictions from our insurance.json flags (III Facts + Statistics: Uninsured Motorists (IRC 2025 study; 2023 data; "20 states and D.C. have mandatory UM or UIM"))
UM: other driver has none (or hit-and-run). UIM: other driver has insurance that is too little for your bill. Both pay you, not the other driver.
III's mandatory-purchase table is not the same as "must be offered" or "included by default unless you reject." Tennessee is the clear example (III Facts + Statistics: Uninsured Motorists (IRC 2025 study; 2023 data; "20 states and D.C. have mandatory UM or UIM") · Tenn. Code § 56-7-1201 (2025) — UM requirements, rejection, umbrella exemption)
In Tennessee, excess/umbrella policies need not include UM/UIM (Tenn. Code § 56-7-1201 (2025) — UM requirements, rejection, umbrella exemption). Ask before you assume — see umbrella UM/UIM.
Type an injury bill, the other driver's bodily-injury (BI) per-person limit, and your UM/UIM per-person limit. We do simple arithmetic: the other driver's insurance pays up to its limit, your UM/UIM may cover the gap up to your limit, and anything left may still be yours to recover somehow (or go unpaid). This is not a claim estimate. Real claims have fault rules, stacking limits, offsets for amounts already collected, medical-payment coordination, and policy exclusions.
III says 20 states and the District of Columbia have mandatory requirements for uninsured or underinsured motorist coverage (III Facts + Statistics: Uninsured Motorists (IRC 2025 study; 2023 data; "20 states and D.C. have mandatory UM or UIM")). The chips below come from our minimum car insurance by state table (checked with III's mandatory-purchase flags and state sources). We list 21 jurisdictions. "Required" here means our data flags UM and/or UIM in the state's required coverages — not every nuance of offer-and-reject law. Tennessee is not in this list: III does not treat TN as a mandatory-purchase state, even though Tenn. Code § 56-7-1201 puts UM on policies by default (see below).
Full per-state liability limits: /insurance/auto. Sources for the mandatory count: III Facts + Statistics: Uninsured Motorists (IRC 2025 study; 2023 data; "20 states and D.C. have mandatory UM or UIM").
Three common patterns show up in primary sources. They are easy to mix up:
UM must be in every auto liability policy issued or renewed in TN, at limits equal to the policy's BI liability, unless the named insured rejects in writing or selects lower limits (not below § 55-12-107). Umbrella/excess need not include UM/UIM. This is different from III's "mandatory purchase" table — TN is not listed there as a state where you cannot reject UM.
Sources: Tenn. Code § 56-7-1201 (2025) — UM requirements, rejection, umbrella exemption · III Facts + Statistics: Uninsured Motorists (IRC 2025 study; 2023 data; "20 states and D.C. have mandatory UM or UIM").
NY DFS: every auto policy must include uninsured-motorist bodily-injury coverage at the same minimums as liability ($25,000 / $50,000). Optional SUM (Supplementary Uninsured/Underinsured Motorists) can be bought up to your BI liability limits; insurers must offer $250,000/$500,000 SUM if your BI limits are that high or higher.
Sources: NY DFS: How much auto insurance must I carry? (UM mandatory at BI minimums; SUM optional).
California DOI (Form 101, revised Feb. 5, 2025): the company must offer UM/UIM. If you do not buy it, you must sign a waiver saying it was offered and you turned it down. UMBI limits match your liability limits; UMPD is capped at $3,500 when the uninsured driver is identified.
Va. Code § 38.2-2206: every auto liability policy must include UM (and matching UIM) at limits that equal — but do not exceed — the policy's liability limits, unless a named insured reduces them (not below financial-responsibility minimums) under the notice rules in § 38.2-2202. Excess/umbrella policies are not required to offer UM/UIM (§ 38.2-2206(J)). Virginia's minimum liability became 50/100/25 on Jan. 1, 2025.
Sources: Code of Virginia § 38.2-2206 — Uninsured motorist insurance coverage · VaultRubric /insurance/auto/virginia — VA minimum liability 50/100/25 as of Jan. 1, 2025 (SCC policy amendment).
Tennessee's verified minimum auto liability is 25/50/25 (checked October 12, 2026; TN minimums page; Tennessee Department of Revenue: Drive Insured Tennessee (liability minimums)). IRC via III estimated Tennessee's uninsured-motorist rate at 21.3% in 2023 — 5th-highest among states and D.C. in the 2023 IRC estimates published via III (III Facts + Statistics: Uninsured Motorists (IRC 2025 study; 2023 data; "20 states and D.C. have mandatory UM or UIM")).
Primary source: Tenn. Code § 56-7-1201 (2025) — UM requirements, rejection, umbrella exemption (2025 Tennessee Code). This is why TN can look "required" in a statute and still sit outside III's mandatory-purchase list.
For a Tennessee reader (and anyone in a state with low BI minimums): Tennessee's minimum BI per person is $25,000 (25/50/25). About 21.3% of Tennessee drivers were estimated uninsured in 2023 (IRC via III). If you face a $100,000 injury bill and the at-fault driver only carries the $25,000 minimum:
Best pick for a Tennessee driver, by the math: a UM limit at least as large as the injury bill you worry about (here $100,000), because Tennessee's offset means the other driver's minimum does not stack on top. That is why matching (or exceeding) a serious injury bill with your UM/UIM limit — and confirming you did not sign a rejection form — matters in the numbers. This is arithmetic for your situation, not a recommendation to buy or sell any policy. Your agent or insurer quotes the premium; your contract decides what pays.
Roadmap — what to do next:
UM (uninsured motorist) pays you when the at-fault driver has no liability insurance or, in many policies, is a hit-and-run. UIM (underinsured motorist) can pay when the at-fault driver has insurance that is too little for your injury bill. Both are for your injuries (and sometimes your property), not for damage you cause to others.
Tenn. Code § 56-7-1201 says every auto liability policy issued or renewed in Tennessee must include UM equal to the policy's bodily injury liability limits, unless the named insured rejects in writing or selects lower limits (not below § 55-12-107 minimums). That is "included by default," not the same as III's mandatory-purchase list — Tennessee is not on that III list. Umbrella policies need not include UM/UIM in Tennessee.
The Insurance Research Council, published via the Insurance Information Institute, estimated 15.4% of U.S. motorists were uninsured in 2023. Tennessee was estimated at 21.3%. Full state list: III's Uninsured Motorists facts page.
III says 20 states and D.C. have mandatory UM or UIM requirements. Our chips list jurisdictions where our insurance.json flags UM and/or UIM. Offer-and-reject rules (like California's waiver, or Tennessee's written rejection) are separate — see the offer/reject section.
Sometimes. Texas's regulator says an umbrella might pay UM/UIM claims; South Dakota warns it is not always included; Nevada requires a signed disclosure. Tennessee law says excess/umbrella need not provide UM/UIM. Ask your insurer. Details: /insurance/umbrella#um.
No. VaultRubric republishes facts from regulators, statutes, and III/IRC with dates, plus arithmetic on sample bills. We don't sell insurance or give quotes.
Facts, not insurance advice. We don't sell insurance or provide quotes; confirm coverage and requirements with the insurer, an agent or your state insurance department.