39 CFR §121.0
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
Service standards in this part are contingent upon proper acceptance before the applicable day-zero Critical Entry Time (CET). Applying the service standards appearing in this part, effective service standards for combinations of 5-digit originating ZIP Codes and 5-digit destinating ZIP Codes can be found in a lookup table at www.usps.com.