Format validation vs registry lookup
The comparison between validating an identifier's structure (format) and querying the authority to verify it exists (registry).
Format validation and registry lookup are two complementary steps that many integrations conflate. Understanding the difference defines which tool to use at each pipeline stage. **Format validation** checks the syntactic structure: correct length, allowed charset, check digit computed by the official algorithm. It's local: no network, no per-request cost, microsecond latency. It catches typos and garbage data, but doesn't guarantee the identifier exists in the real world. **Registry lookup** asks the issuing authority directly (AFIP, Receita Federal, SAT, RENAPER) whether the identifier has been issued and is active. It carries latency (100–2000 ms), per-query cost, and dependencies on the authority's uptime. It returns real data: holder name, tax status, issue date. **The recommended strategy**: validate format first, registry lookup second. Format validation rejects ~10–20% of bad inputs without spending paid queries. Only those that pass the structural filter justify a registry call. Normadata covers the first step for 17 identifiers across 10 countries. For the second, specialized providers exist per country (Idwall in Brazil, Truora across LATAM, AFIP scrapers in Argentina). The combination yields the best cost/quality ratio.