Checksum first, registry next

🪪 Tax ID Validator & Lookup

Validate a Vietnamese tax ID (10 or 13 digits) against its official weighted checksum with every multiplication shown — then press Look up to fetch the registered name, address, tax department and operating status straight from the tax registry.

Tax ID — 10 digits, or 13 as NNNNNNNNNN-NNN

Checksum rule: N₁₀ = 10 − (31·N₁+29·N₂+23·N₃+19·N₄+17·N₅+13·N₆+7·N₇+5·N₈+3·N₉) mod 11. Checking runs entirely in your browser; only when you press Look up is the tax ID sent to the public registry API (xinvoice.vn, limit ~10 lookups / 30s).