/**
 * RFC (Registro Federal de Contribuyentes) normalizer · México
 *
 * Reference: Servicio de Administración Tributaria (SAT) · https://www.sat.gob.mx
 * Format:
 *   - Persona moral: 12 characters (3 letters + 6 digits + 3 alphanum)
 *   - Persona física: 13 characters (4 letters + 6 digits + 3 alphanum)
 *
 * RFC homoclave (last 3 chars) is computed by SAT; we validate format
 * only · checksum verification requires the SAT-internal algorithm.
 */
/**
 * Normalize a Mexican RFC to canonical uppercase form (no spaces, no hyphens).
 */
export declare function normalizeRfcMX(input: string): string;
/**
 * Return the RFC kind (moral for empresas · física for personas) or null
 * if the input does not match either format.
 */
export declare function rfcKindMX(input: string): 'moral' | 'fisica' | null;
/**
 * Validate the format of a Mexican RFC. Does NOT verify the SAT homoclave
 * checksum (which requires a proprietary algorithm).
 */
export declare function isValidRfcMX(input: string): boolean;
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