Employers must query the Clearinghouse at least once a year for every driver they employ who is subject to drug and alcohol testing (49 CFR 382.701(b)).

• A limited query with the driver's general consent usually meets the requirement.
• If the limited query shows that information exists, the employer must run a full query within 24 hours. If it does not, the driver must not perform safety-sensitive functions until the full query shows no prohibition.