The 25-year rule

• NHTSA / DOT: 49 CFR 591.5(i)(1) allows import of a vehicle that is "25 or more years old" without meeting FMVSS. Source: eCFR. ImportClock models age from each car's own build month (our working assumption, not a quote from that section); confirm with NHTSA.
• EPA: Form 3520-1 code E: at least 21 years old (calendar year of manufacture subtracted from calendar year of import), original unmodified configuration; customs may require proof of age. Source: EPA Form 3520-1.
• CBP: must file EPA 3520-1 and DOT HS-7 at entry. Source: CBP.
• States have separate rules: see state guides.