What is the format of a Swiss IBAN?

A Swiss IBAN is always exactly 21 characters: the two-letter country code CH, two check digits, a 5-digit IID (Institut-Identifikation, the Swiss bank clearing number), and a 12-character alphanumeric account number. The IID section contains only digits; the account number may include uppercase letters A-Z as well as digits 0-9. Switzerland uses 21 characters — one fewer than Germany (22) and two fewer than France (27).

What is an IID (Institut-Identifikation)?

The IID is the 5-digit Swiss interbank clearing number maintained by the Swiss National Bank (SNB). It uniquely identifies the paying institution in the Swiss Interbank Clearing (SIC) system. Well-known IIDs include 09000 for PostFinance, 00230-00260 ranges for UBS, and 08401 for Zürcher Kantonalbank. The IID in an IBAN corresponds directly to the BIC/SWIFT bank identifier used internationally.

How does ISO 7064 MOD-97-10 validation work for Swiss IBANs?

The algorithm moves the first four characters (CH plus the two check digits) to the end of the string, then converts every letter to its two-digit numeric code (A=10, B=11, ... Z=35, so C=12 and H=17). The resulting very long number is divided by 97 using progressive folding — processing one digit at a time — to avoid any integer overflow. A valid IBAN always produces a remainder of exactly 1.

Why does the account number contain letters?

Swiss IBANs embed the traditional account number exactly as the bank assigned it. Some Swiss banks — notably PostFinance and several cantonal banks — use alphanumeric account formats that include uppercase letters. The BBAN specification in the SWIFT IBAN Registry explicitly allows letters in positions 10-21 for Switzerland, which is why the validator accepts A-Z as well as 0-9 in that section.

Does a valid result mean the account exists?

No. A pass means the IBAN is structurally and mathematically well-formed according to the SWIFT IBAN Registry and ISO 7064 MOD-97-10. It cannot confirm that the account is open, has funds, or belongs to any particular person. Only the bank identified by the IID can verify account existence, and even then only through official channels.

Is this tool safe to use with real account numbers?

Yes — everything runs locally in your browser. The IBAN you enter is never transmitted to any server, logged, or stored. The source code processes the string entirely in JavaScript running on your own device. You can disconnect from the internet before using the tool and it will work identically.

Swiss IBAN Validator

The Swiss IBAN Validator checks whether a Swiss bank account number in IBAN format is structurally correct. It verifies the CH country code, the total 21-character length, the 5-digit IID (Institut-Identifikation) clearing number, the 12-character alphanumeric account number, and the full ISO 7064 MOD-97-10 checksum — all without sending a single character to a server.

Swiss IBANs became mandatory for cross-border SEPA payments and are now the standard format for domestic wire transfers and payment slips (QR-bill) in Switzerland. With Switzerland ranking among the world’s leading financial centres, valid IBAN handling is critical for banks, payroll providers, fintech integrations, and any business accepting CHF payments from Swiss accounts. A quick offline check catches transposition errors and paste mistakes before they reach payment rails.

How it works

A Swiss IBAN has a precisely defined structure laid out in the SWIFT IBAN Registry:

CH — the ISO 3166-1 alpha-2 country code for Switzerland (always uppercase)
kk — 2 check digits computed by the ISO 7064 MOD-97-10 algorithm
bbbbb — the 5-digit IID (Institut-Identifikation), the Swiss Interbank Clearing participant number
cccccccccccc — the 12-character account number (digits 0-9 and uppercase letters A-Z)

Total: 21 characters.

The checksum calculation follows ISO 13616 / ISO 7064 MOD-97-10 exactly:

Strip spaces and convert to uppercase.
Verify the string starts with CH and is exactly 21 characters.
Confirm positions 5-9 are all digits (the IID) and positions 10-21 are alphanumeric.
Move the first four characters (CH plus check digits) to the end of the string.
Replace each letter with its 2-digit numeric code: C = 12, H = 17 (producing 1217 for CH).
Interpret the result as an integer and compute the remainder when divided by 97, using progressive folding to avoid overflow.
The IBAN is valid if and only if the remainder equals 1.

The tool also maps the 5-digit IID to a bank name using a curated lookup table of Swiss Interbank Clearing participants, so you can visually confirm the right institution is encoded.

Worked example

Take the canonical Swiss test IBAN CH56 0483 5012 3456 7800 9:

Country code: CH — Switzerland
Check digits: 56
IID: 04835 — PostFinance AG
Account number: 012345678009

To verify the checksum, move CH56 to the end: 048350123456780091256.

Expand letters: C = 12, H = 17, giving the numeric string 04835012345678009121756.

Fold this over mod 97: the remainder is 1, confirming the IBAN is valid.

Field	Value	Meaning
Country	CH	Switzerland
Check digits	56	MOD-97 checksum pair
IID	04835	PostFinance AG clearing number
Account number	012345678009	Account at PostFinance
Total length	21	Matches the SWIFT registry

Any single-digit change to a valid IBAN almost always produces a remainder other than 1, which is why the checksum catches the vast majority of typos and transpositions.

Every character is processed locally in your browser — nothing is uploaded, logged, or transmitted at any point.