/** ISO 7812 / Luhn. Used by payment cards, IMEIs and a few national ids. */
export declare function isValidLuhn(digits: string): boolean;
/**
 * The published length of an IBAN per country. This is not decoration: the
 * checksum alone accepts a truncated IBAN often enough to matter, and the
 * length is what stops the scanner from swallowing the next number on the line.
 */
export declare const IBAN_LENGTHS: Readonly<Record<string, number>>;
/**
 * ISO 13616 check: move the first four characters to the end, replace every
 * letter by its position in the alphabet plus 9, and the result must be
 * congruent to 1 mod 97.
 *
 * The remainder is taken nine digits at a time. The whole number would overflow
 * a double long before a 34-character IBAN is finished, and doing it in BigInt
 * would cost an allocation per candidate for arithmetic that fits in an int.
 */
export declare function isValidIban(candidate: string): boolean;
/**
 * ISO 7064 MOD 11,10 — the check digit of the German Steuerliche
 * Identifikationsnummer (IdNr).
 */
export declare function iso7064Mod1110(digits: string): number;
/**
 * German tax id: eleven digits, and two rules that are easy to miss.
 *
 * The check digit is only half of it. The Bundeszentralamt für Steuern also
 * guarantees a *repetition* rule over the first ten digits — exactly one digit
 * occurs twice or three times and the rest at most once — which is what makes
 * a plain counter or a padded phone number fail here even when its check digit
 * happens to land right.
 */
export declare function isValidGermanTaxId(digits: string): boolean;
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