Unified social credit code checker: China USCI validation

Paste the 18-character code from a Chinese business licence. This page splits it into the five parts defined by GB 32100-2015 and recalculates the check digit. The code is not sent to a server by this calculation. The implementation was run against 2,149 real codes from two official Chinese disclosure files: all 2,149 came back consistent.

How the 18 characters are built

GB 32100-2015 fixes both the length and the layout. For a supplier, ask for its current business licence to obtain the code. Asking matters because a name often will not do: in a frame of 310 Chinese company names printed on US recall notices, 167 matched no registry record at all.

What the first two characters tell you

Position 1 is the registration authority and position 2 is the entity category under it. The pairing most buyers care about sits under market regulation (code 9):

Read the first two-character prefix together: position 1 identifies the registration authority and position 2 the entity category under it.

The prefix does not establish export eligibility. It identifies the registered entity category. Check the goods, destination, customs requirements and the roles of the parties separately.

Other authorities appear in the first position too: 1 for centrally staffed bodies, 5 for civil-affairs registrations such as foundations and social organisations, N for rural collective economic organisations, and several more.

Where it is registered

Positions 3–8 identify the registration authority’s administrative division. This tool decodes only the first two digits, such as 11 Beijing or 44 Guangdong. It does not validate the full city or county code. The prefix is not evidence of a factory’s location.

This tool maps 71, 81 and 82 to Taiwan, Hong Kong and Macau. A displayed region label is not a check that the full administrative code was assigned to this entity.

Character set

Codes use digits and uppercase letters, but the standard excludes I, O, Z, S and V and gives no reason. The usual explanation is that they look like 1, 0, 2, 5 and U. If you see one, compare with the source document. This check cannot distinguish a typo from an altered document.

Check digit

The eighteenth character is calculated from the first seventeen. Each position has a weight of 3⁽ⁱ⁻¹⁾ mod 31, and the check character satisfies C18 = 31 − (Σ Ci × Wi mod 31), taken modulo 31 so that a result of 31 becomes 0. A single mistyped character will therefore almost always fail.

Worked examples

Four codes through the same rule. Paste any of them into the checker above to see the same result. These codes are constructed for illustration, with check digits computed by this implementation. They are not presented as real companies.

A valid enterprise code. 91330106MA27XNEX2L passes.

• 9 then 1: registered by the market regulation authority as an enterprise (企业).
• 33 in positions 3 to 8: registered in Zhejiang.
• L at position 18 matches the calculation from the first 17 characters.
• Passing proves the structure and check digit are consistent. It does not prove this company exists or is active.

One wrong character fails. Take the valid code above and change only the last character from L to 9: it now fails.

• The calculation expects L at position 18, so the check digit fails. A single mistyped character is caught.
• If a supplier’s code fails like this, compare it with the licence character by character.

An excluded character stops the check. 91330106MA27XNES2L is rejected.

• It contains S. GB 32100-2015 excludes I, O, Z, S and V and gives no reason for it.
• The code fails on the character set before the check digit is even calculated. Compare with the source document.

A passing code is not always a company. 92370900MA3C8KQ61D passes, and it is not a company.

• 9 then 2: an individually-owned business (个体工商户), a different legal form from an enterprise.
• 37 in positions 3 to 8: registered in Shandong. The check digit D is consistent, so the code passes.
• Passing means only that the arithmetic holds. The second character already tells you the legal form of the counterparty.

What a passing code proves, and what it does not

Use the result to check the number, then gather evidence for the company and transaction.

China tax ID. For a company or other organisation that holds this code, it is also the taxpayer identification number. State Taxation Administration Announcement 2015 No. 66 sets this. A business without the code uses an ID document number plus two digits.

It proves

• The check character agrees with the calculation from the first 17 characters.
• The input has 18 characters from the permitted set.

It does not prove

• That the company exists. A correctly formed code can be constructed by anyone who knows the algorithm, including the one on this page.
• That the company is still active and has not been revoked or deregistered.
• That its registered business scope covers what you are buying.
• That it may legally export to you. The code does not contain the goods, destination or transaction-specific permissions.
• That this company is the one issuing your invoice or receiving your payment. Document each party’s role and explain any differences before paying.

A dated registry record helps confirm the legal identity. Other questions need transaction documents, account checks or product-specific advice. The official China company registry steps show the route, including what to do when the portal will not open from where you are.

How to calculate the check character by hand

The 18th character of a Unified Social Credit Code is 31 minus the remainder of a weighted sum divided by 31. The sum multiplies the value of each of the first 17 characters by a fixed weight for its position.

Step 1: character values

Digits keep their own value. The 21 permitted letters take the values 10 to 30 in alphabetical order, with I, O, Z, S and V left out.

Step 2: position weights

Each of the 17 positions has its own weight. The weight for position i is 3 raised to the power i minus 1, taken modulo 31.

Step 3: multiply, add and take the remainder

Multiply each character value by its weight and add the 17 products. The example below is the one printed in Appendix B of GB 32100-2015, for the first 17 characters 91350100M000100Y4.

The products add up to 1640. 1640 divided by 31 leaves a remainder of 28, so the check value is 31 minus 28, which is 3. Value 3 is the character 3, and the full code is 91350100M000100Y43.

The checker above returns the same result for 91350100M000100Y43. It also validated all 2,149 real codes in the test sample.

Two special results

A remainder of 0 gives 31, which is written as 0. A remainder of 1 gives 30, which is written as Y. The constructed code 91330106MA27XNEXG0 ends in 0 and 91330106MA27XNEXTY ends in Y.

Both codes are constructed for illustration with the calculation above. They are not real companies.

Every code in positions 1 to 8

Position 1 of a Unified Social Credit Code names the registration authority, and position 2 names the entity category under it. GB 32100-2015 lists 12 authorities and 36 two-character prefixes in the version amended in 2016.

Positions 1 and 2: authority and entity category

A prefix such as 91 reads as authority 9 (market regulation) and category 1 (enterprise). Amendment No. 1, approved on 15 April 2016 and in force from 18 April 2016, added the authorities 2, 3, 4, 6, 7, 8, A and N to the four in the first edition.

Buyers meet 91 most often. A prefix shows the category at the time the code was assigned, and the code anatomy study explains why it can be out of date.

Positions 3 to 8: province and district

Positions 3 to 8 hold the administrative division code of the registration authority, taken from GB/T 2260. The first two digits name the province-level unit, such as 44 for Guangdong or 31 for Shanghai.

Digits 5 to 8 continue to city and county level and change when boundaries change, so the checker decodes only the province. The prefix shows where the registration authority sits. It does not show where a factory stands.

Why a code fails the check

The checker reports one of four failures: wrong length, an excluded letter, a symbol outside the character set, or a wrong 18th character. Most failures are a single mistyped character.

A failed check almost always means one wrong character. Compare the code with the licence character by character. If the code matches the licence, look the company up by name, because the registry record does not depend on this arithmetic.

Common questions

What is a Unified Social Credit Code?

An 18-character identifier for a registered mainland Chinese entity. It contains authority, entity category, administrative division, subject identifier and check-character fields.

How do I verify a Chinese Unified Social Credit Code?

First check the length, character set and check character. Then compare the exact code and legal name with a dated registry record. Passing the arithmetic check does not confirm correct copying or company identity.

What do the first two characters of the code mean?

Position 1 is the registration authority and position 2 is the entity category. Under authority 9, codes starting 91 describe enterprises, 92 individually-owned businesses and 93 farmers’ specialised cooperatives.

Does a valid code mean the company is real?

No. A code can be constructed to pass the check. It does not prove company existence, current status, account ownership or permission to export.

How many characters does a Unified Social Credit Code have?

18. The characters are digits and uppercase letters, and the letters I, O, Z, S and V are never used.

Why does a Unified Social Credit Code never contain I, O, Z, S or V?

GB 32100-2015 lists these five letters as unused and gives no reason. The usual explanation is that they look like the digits 1, 0, 2 and 5 and the letter U.

How is the 18th character of a Unified Social Credit Code calculated?

Multiply the value of each of the first 17 characters by its weight, add the products and take the remainder after dividing by 31. The check character is the one with the value 31 minus that remainder, written as 0 for a remainder of 0 and Y for a remainder of 1.

What does a Unified Social Credit Code that starts with 91 mean?

91 means the code was assigned under the market regulation authority (position 1 is 9) to an enterprise (position 2 is 1). 92 is an individually-owned business and 93 is a farmers’ specialised cooperative.

Is the Unified Social Credit Code the same as the Chinese tax ID?

Yes, for an organisation that holds one. State Taxation Administration Announcement 2015 No. 66 makes the code the taxpayer identification number of that organisation.

Does a Unified Social Credit Code ever change?

GB 32100-2015 defines it as a legal identification code that is unique nationwide and does not change for the life of the legal entity or other organisation. A supplier that quotes a different code on a later document needs to explain the difference.

Which part of a Unified Social Credit Code shows the province?

Positions 3 to 8 hold the administrative division code of the registration authority, taken from GB/T 2260. The first two of those digits give the province-level unit, such as 44 for Guangdong. They show where the code was registered and do not show where a factory stands.

Why does my Unified Social Credit Code fail the check?

Most failures are one wrong character among the 18, and the checker also stops on the wrong length or on the letters I, O, Z, S and V. Compare the code with the licence character by character, then look the company up by name if it still fails.

How this implementation was tested

The implementation uses the GB 32100-2015 character set and weight formula. We checked the formula and tested codes extracted from two official disclosure files.

On 11 August 2026, 2,149 real Unified Social Credit Codes from Ministry of Finance and Shanghai Municipal Tax Service disclosure files were tested. All 2,149 returned a consistent check digit. This is evidence about that sample; it does not prove the implementation has no errors or validate every possible code.

On 30 September 2026 we also recalculated the worked example printed in Appendix B of GB 32100-2015. The implementation turns 91350100M000100Y4 into check character 3, as the standard does. The step-by-step calculation shows every product.

The sample checks arithmetic consistency. It does not establish any company’s current status, and this page queries no registry.

Open source, and citing this checker

The same check is published as an open-source package, china-usci on npm (MIT licence, no runtime dependencies, Node 18 or later, source on GitHub). It applies the same GB 32100-2015 check and states the same limit as this page: a passing check character says nothing about whether the company exists.

Install it with npm install china-usci or pnpm add china-usci, or try one code without installing: npx china-usci 91350100M000100Y43. Read the package’s changelog and tests before using it in your own system.

To cite the checker, include its title, URL and the date you used it:

Currawong, “Unified social credit code checker: China USCI validation”, free in-browser validation of the 18-character code structure and the GB 32100-2015 check digit, tested on 2,149 real codes. https://currawongweb.com/verify/china-usci-checker/