New Hampshire DWI Laws Explained

By Javier Marín, Editor·Last reviewed September 2026·How we check this

New Hampshire calls the offense DWI — Driving While Intoxicated — under RSA 265-A, not DUI. A DWI arrest in New Hampshire is technically a "complicated misdemeanor" by statute, which gives the offense more procedural and evidentiary weight than an ordinary misdemeanor and produces a longer license suspension and a heavier fine. The case automatically becomes eligible for expungement after 10 years.

The legal threshold

New Hampshire DWI thresholds:

Adults 21+: 0.08% BAC.
Aggravated DWI: 0.16% BAC or higher.
Drivers under 21: 0.02% BAC — see the under-21 conduct rules in Youth Operator License.
Commercial drivers (CDL): 0.04% BAC.
Drugs or impairing substances: no per-se threshold; impairment is established through officer observation, Standardized Field Sobriety Tests, and Drug Recognition Expert evaluations.

New Hampshire allows convictions on either the per-se BAC or on impairment evidence alone — even below 0.08%.

First-offense penalties

A first New Hampshire DWI conviction (without aggravators) carries:

A fine of $500 to $1,200 plus a 24% penalty assessment.
A 9-month minimum license suspension; up to 2 years.
Mandatory completion of an Impaired Driver Care Management Program (IDCMP) that includes a substance-use evaluation and any treatment or education the evaluator recommends.
SR-22 financial responsibility filing for 3 years from the reinstatement date — see New Hampshire car insurance.
Possible installation of an Ignition Interlock Device (IID) for the period of any restricted license.

Aggravated DWI

A DWI is "aggravated" under RSA 265-A:3 when any of these apply:

BAC at or above 0.16%.
Driving more than 30 mph over the posted speed limit while intoxicated.
Causing a serious bodily injury accident while intoxicated.
Operating a vehicle while attempting to flee a law enforcement officer.
Carrying a passenger under age 16 while intoxicated.

An aggravated DWI conviction carries a fine of $750 to $2,000, mandatory minimum jail time of 17 days (5 days if completed at a residential treatment facility), an IID requirement, and an 18-month to 2-year license revocation.

Implied consent and chemical-test refusal

New Hampshire's implied consent law (RSA 265-A:4) requires every driver to submit to chemical testing — breath, blood, or urine — when arrested for DWI. Refusing the test triggers an automatic administrative license suspension:

180 days for a first refusal.
2 years for a second or subsequent refusal.

The administrative suspension runs separately from any criminal-court suspension and applies even if the criminal case is dismissed. The driver has 30 days from the arrest to request an administrative hearing before the NH DMV's Bureau of Hearings.

Ignition Interlock Devices (IID)

An IID is required as a condition of any limited or restricted license issued during a DWI suspension, and for the full duration of any aggravated DWI license revocation. The device is installed at the driver's expense (typically $70-$150 per month plus a $100-$150 install fee) and prevents the vehicle from starting if the driver's breath shows alcohol. IIDs collect rolling-test data that the installer reports to the NH DMV; failed tests can extend the IID period.

Repeat offenses

A second DWI within 10 years of a first conviction carries a fine of $750 to $2,000, mandatory minimum jail time, an IID requirement, and a 3-year license revocation. A third DWI within 10 years is a Class B felony — up to 7 years in state prison, indefinite license revocation, and lifetime IID requirement on any future restricted license.

Automatic expungement

New Hampshire is unusual in providing for automatic expungement of a first-offense DWI conviction 10 years after the date of conviction, provided no further DWI convictions have occurred during that period. The expunged record is no longer reported on standard background checks, although the underlying court file remains accessible to law enforcement and certain government agencies. For driving record purposes, see New Hampshire driver records and suspended license.