. • https://www.oecd.org/content/dam/oecd/en/topics/policy-issue-focus/aeoi/austria-tin.pdf Belgium Numéro National (NN) (French) / Rijksregisternummer (RRN) (Dutch) / National Number Digits: 11-digit Format: YY. MM. DD-XXX. CC or as a single block of 11 digits (for IT processing). In Belgium, your TIN corresponds to your national register number.