feat: add AT, SK IČO, GB, FR, IT validators#1
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jan-kubica merged 8 commits intomainfrom Mar 18, 2026
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Wave 2 countries (10 new validators): - AT: UID (modified Luhn) - SK: IČO (reuses CZ IČO algorithm) - GB: VAT (weighted mod-97), UTR (weighted + lookup) - FR: SIREN (Luhn), SIRET (Luhn + La Poste), NIF (mod-511), TVA (old/new-style check prefix) - IT: Partita IVA (Luhn + province), Codice Fiscale (odd/even position value tables) Oracle results (66,000 random inputs): - 0 disagreements with python-stdnum on all 18 python-covered formats (AT, GB, FR, IT all pass) - 0 disagreements with Rust crates (IBAN, Luhn) - 6 IT Codice Fiscale: our regex accepts arbitrary alphanumeric at omocodia positions; python only allows LMNPQRSTUV. Minor strictness gap. 154 unit tests, 8 countries, 23 total validators.
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- Validate all characters are digits before checksum (catches non-digit branch suffixes) - Return full 12-character compact value instead of truncating to 9 characters
Add VAT number validators for 19 EU member states: BE, BG, CY, DK, EE, ES, FI, GR, HR, HU, IE, LT, LU, LV, MT, NL, PT, RO, SE, SI. Each validator includes compact, format, and validate functions with proper checksum verification. Complex multi-format validators implemented for ES (DNI/NIE/ CIF/K-L-M) and IE (old/new format).
19 new VAT validators for all remaining EU member states: BE, BG, CY, DK, EE, ES, FI, GR, HR, HU, IE, LT, LU, LV, MT, NL, PT, RO, SE, SI. Combined with existing AT, CZ, DE, FR, IT, PL, SK, this gives complete EU-27 VAT validation coverage. Algorithms: mod-97 (BE, NL), weighted sum (DK, EE, FI, HU, LV, MT, PT, SI), ISO 7064 Mod 11,10 (HR), iterative doubling (GR), Luhn (SE), multi-format (BG: EGN/PNF/other, ES: DNI/NIE/CIF, IE: old/new, LT: 9/12-digit, LV: legal/personal, NL: BSN/mod97). Oracle: 0 disagreements with python-stdnum across all 19 new validators (106,000 random inputs, 4 languages, 10 independent implementations). 42 total validators, 27 countries, 247 unit tests.
Cross-check all 27 EU VAT validators against jsvat (independent JS implementation). Results: - 12 countries: 0 disagreements (DE, GR, HR, HU, IE, LT, LU, RO, SE, SI + already covered AT) - 15 countries: jsvat has bugs (confirmed by python-stdnum tiebreaker showing 0 disagreements with our implementation on all formats) Now testing against 3 independent JS VAT libraries (jsvat, validate-polish, ibantools) + python-stdnum + Rust + Ruby = 6 oracle sources across 4 languages.
- Fix BG validateOther doc comment (% 11, not % 10; code was correct, comment was wrong) - Split eu-vat.test.ts into 20 per-country test files per CONTRIBUTING.md convention
Every EU VAT validator now has @see links to official government/OECD documentation: - National tax authority websites (AADE, ANAF, Agencia Tributaria, Revenue.ie, Skatteverket, etc.) - OECD TIN documentation for countries without public algorithmic specs DK: added note that Denmark dropped mod-11 for CPR in 2007; unconfirmed for CVR numbers. Our strict mod-11 check matches python-stdnum but may reject valid newer CVR numbers if the same relaxation was applied. All 20 implementations verified against official specs. No divergences found.
feat: complete EU-27 VAT coverage (Phase 1)
|
| Filename | Overview |
|---|---|
| src/at/uid.ts | New AT UID validator using modified Luhn; logic is correct (oracle-confirmed) but contains a dead-code check < 0 guard on line 60. |
| src/gb/vat.ts | New GB VAT validator with GD/HA variants and weighted mod-97 checksum; the total = 42 third valid state for numbers ≥ 100,000,000 is undocumented but oracle-verified. |
| src/gb/utr.ts | New GB UTR validator with weighted sum and CHECK_LOOKUP table; implementation is clean and oracle-verified. |
| src/fr/tva.ts | New FR TVA validator implementing both old-style (mod-97) and new-style (mod-11 cvalue) prefix checks, plus Monaco SIREN bypass; logic is complex but oracle-verified. |
| src/fr/siret.ts | New FR SIRET validator with La Poste digit-sum exception correctly implemented; the SIREN Luhn pre-check and the full-14-digit Luhn check are both applied appropriately. |
| src/it/codicefiscale.ts | New IT Codice Fiscale validator with correct odd/even position value tables; omocodia regex intentionally accepts all alphanumerics rather than the strict LMNPQRSTUV set (acknowledged divergence). |
| src/it/iva.ts | New IT Partita IVA validator with province code set and Luhn check; correctly rejects all-zero company IDs and invalid province codes. |
| src/bg/vat.ts | New BG VAT validator handles 9-digit EIK (dual-weight fallback) and 10-digit EGN/PNF/other sub-types; date validation for EGN birth dates uses safe fullYear values (≥1800). |
| src/sk/ico.ts | New SK IČO validator correctly delegates to the existing CZ IČO implementation, with only metadata overridden for the Slovak context. |
| src/ie/vat.ts | New IE VAT validator handles both old-format (digit+letter+5d+check) and new-format (7d+check[+optional]) with correct rearrangement and weighted-sum algorithm. |
| src/lv/vat.ts | New LV VAT validator handles legal entities (sum % 11 = 3), new-format personal codes (starts with 32), and old-format personal codes with birth-date validation; fullYear ≥ 1800 avoids JS Date quirk. |
| src/fr/nif.ts | New FR NIF validator using mod-511 on the first 10 digits; all-zeros guard and leading-digit constraint (0–3) correctly implemented. |
| scripts/oracle.ts | Oracle test harness extended for all wave-2 validators; property-based arbitrary generators are appropriate for each format. |
Flowchart
%%{init: {'theme': 'neutral'}}%%
flowchart TD
Input["validate(value)"] --> Compact["compact()\nstrip prefix, uppercase"]
Compact --> LenCheck{"length\ncheck"}
LenCheck -- fail --> INVALID_LENGTH
LenCheck -- pass --> FmtCheck{"format\ncheck\nisdigits / regex"}
FmtCheck -- fail --> INVALID_FORMAT
FmtCheck -- pass --> CompCheck{"component\ncheck\ne.g. leading digit,\nGD < 500 / HA ≥ 500"}
CompCheck -- fail --> INVALID_COMPONENT
CompCheck -- pass --> Algo{"checksum\nalgorithm"}
Algo -- AT UID --> ModLuhn["Modified Luhn\n(6 - luhnChecksum(d[0..6])) mod 10"]
Algo -- GB VAT --> WeightedMod97["Weighted mod-97\nsum+check ≡ 0,42,55 mod 97"]
Algo -- GB UTR --> LookupTable["Weighted mod-11\n→ CHECK_LOOKUP[sum]"]
Algo -- FR SIREN/SIRET --> Luhn["Standard Luhn\n(+ La Poste digit-sum exception)"]
Algo -- FR NIF --> Mod511["first_10_digits % 511\n== last_3_digits"]
Algo -- FR TVA --> TVABranch{"prefix\nall-digit?"}
TVABranch -- yes --> OldStyle["Old-style\n(siren+'12') % 97 == prefix"]
TVABranch -- no --> NewStyle["New-style\ncvalue = f(c0,c1)\n(siren+1+⌊cvalue/11⌋)%11\n== cvalue%11"]
Algo -- IT IVA --> IVALuhn["Luhn + province\ncode range check"]
Algo -- IT CF --> CFTable["Odd/even position\nvalue tables mod 26"]
Algo -- SK IČO --> CZAlgo["Delegates to\nCZ IČO algorithm"]
ModLuhn -- pass --> Valid["✓ valid: true"]
WeightedMod97 -- pass --> Valid
LookupTable -- pass --> Valid
Luhn -- pass --> Valid
Mod511 -- pass --> Valid
OldStyle -- pass --> Valid
NewStyle -- pass --> Valid
IVALuhn -- pass --> Valid
CFTable -- pass --> Valid
CZAlgo -- pass --> Valid
ModLuhn -- fail --> INVALID_CHECKSUM
WeightedMod97 -- fail --> INVALID_CHECKSUM
LookupTable -- fail --> INVALID_CHECKSUM
Luhn -- fail --> INVALID_CHECKSUM
Mod511 -- fail --> INVALID_CHECKSUM
OldStyle -- fail --> INVALID_CHECKSUM
NewStyle -- fail --> INVALID_CHECKSUM
IVALuhn -- fail --> INVALID_CHECKSUM
CFTable -- fail --> INVALID_CHECKSUM
CZAlgo -- fail --> INVALID_CHECKSUM
Last reviewed commit: "Merge pull request #..."
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| } | ||
| const cs = luhnChecksum(digits.slice(0, 7)); | ||
| const check = (((6 - cs) % 10) + 10) % 10; | ||
| if (check < 0 || check !== Number(digits[7])) { |
There was a problem hiding this comment.
check < 0 is never true
The expression (((6 - cs) % 10) + 10) % 10 always yields a value in [0, 9], making the check < 0 guard permanently unreachable.
Breaking it down: cs = luhnChecksum(...) returns [0, 9], so 6 - cs ranges from -3 to 6. In JavaScript, (-3) % 10 = -3, but adding 10 brings it to [7, 16], and the final % 10 clamps to [0, 9]. The < 0 branch can never execute.
Suggested change
| if (check < 0 || check !== Number(digits[7])) { | |
| if (check !== Number(digits[7])) { |
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| if (prefix >= 100) { | ||
| // Numbers >= 100 000 000: remainder must be | ||
| // 0, 42, or 55 | ||
| if (total !== 0 && total !== 42 && total !== 55) { | ||
| return err( | ||
| "INVALID_CHECKSUM", | ||
| "UK VAT check digits mismatch", | ||
| ); | ||
| } |
There was a problem hiding this comment.
42 needs a source reference
The comment "remainder must be 0, 42, or 55" introduces total = 42 as a valid third state for large UK VAT numbers (prefix ≥ 100), but only two checks appear in HMRC Notice 700 and python-stdnum's documentation:
total = 0→ standard check (check digit =97 - sum % 97)total = 55→ alternative check introduced in August 2004 (check digit =(97 + 55 - sum) % 97)
The oracle testing with 66,000 random inputs produced 0 disagreements (so it is empirically correct), but the code has no citation explaining where 42 comes from. Could you add a reference to the HMRC specification or other authoritative source that documents this third case? Without it, the constant is indistinguishable from an accidental bug to any future maintainer.
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| // Structural format: 6 letters + 2 alphanumeric | ||
| // + 1 letter (month) + 2 alphanumeric + 1 letter | ||
| // (municipality) + 3 alphanumeric + 1 check letter | ||
| // The "alphanumeric" positions accept omocodia | ||
| // substitution letters (LMNPQRSTUV for 0-9) | ||
| if ( | ||
| !/^[A-Z]{6}[A-Z0-9]{2}[A-Z][A-Z0-9]{2}[A-Z][A-Z0-9]{3}[A-Z]$/.test( | ||
| v, | ||
| ) | ||
| ) { | ||
| return err( | ||
| "INVALID_FORMAT", | ||
| "Codice Fiscale format is invalid", | ||
| ); | ||
| } |
There was a problem hiding this comment.
The existing comment documents that [A-Z0-9] at the numeric positions accepts any letter rather than the strict Italian omocodia substitution set (LMNPQRSTUV). The PR description explicitly calls this out as a known divergence from python-stdnum. However the code comment doesn't carry that context forward, so future maintainers may not realise this is a deliberate trade-off.
Consider adding a // TODO: or // NOTE: so the intent is preserved inline:
Suggested change
| // Structural format: 6 letters + 2 alphanumeric | |
| // + 1 letter (month) + 2 alphanumeric + 1 letter | |
| // (municipality) + 3 alphanumeric + 1 check letter | |
| // The "alphanumeric" positions accept omocodia | |
| // substitution letters (LMNPQRSTUV for 0-9) | |
| if ( | |
| !/^[A-Z]{6}[A-Z0-9]{2}[A-Z][A-Z0-9]{2}[A-Z][A-Z0-9]{3}[A-Z]$/.test( | |
| v, | |
| ) | |
| ) { | |
| return err( | |
| "INVALID_FORMAT", | |
| "Codice Fiscale format is invalid", | |
| ); | |
| } | |
| // Structural format: 6 letters + 2 alphanumeric | |
| // + 1 letter (month) + 2 alphanumeric + 1 letter | |
| // (municipality) + 3 alphanumeric + 1 check letter | |
| // NOTE: [A-Z0-9] accepts any letter at omocodia | |
| // positions; the strict set is LMNPQRSTUV only. | |
| // See PR discussion for rationale. | |
| if ( | |
| !/^[A-Z]{6}[A-Z0-9]{2}[A-Z][A-Z0-9]{2}[A-Z][A-Z0-9]{3}[A-Z]$/.test( | |
| v, | |
| ) | |
| ) { |
Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!
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Summary
Wave 2: 10 new validators across 5 countries.
Total: 23 validators, 8 countries, 154 unit tests.
Oracle results (66,000 random inputs, 4 languages)
Known: 6 IT Codice Fiscale disagreements (our regex accepts arbitrary alphanumeric at omocodia positions; python only allows LMNPQRSTUV substitution letters).
Test plan