To generate a valid bank account number, you need to follow the rules of a specific country or financial institution. The structure and verification methods of bank account numbers vary greatly from region to region. The following are the key points and general methods： --- ###**1. The basic composition of the bank account number** Most bank account numbers contain the following parts (the specific order and length vary by country/bank)： 1. **Bank Code (Bank Code)**: Identifies a bank or financial institution (such as the first few digits of the “joint bank number” in China or the “Routing Number” in the United States). 2. **Branch Code (Branch Code)**: Identify a specific branch or outlet. 3. **Account types**: such as savings accounts, public accounts, etc. 4. **Customer account number**: The user's unique account ID. 5. **Check digit**: The result of the algorithm used to verify the validity of the account. --- ###**2. Bank account rules in common countries** #### **1. China** -**Structure**: Usually 19 digits (some banks may be different). -**Composition**： -The first 6 digits: the identity of the issuing bank (for example, China Construction Bank starts with “622700"). -Middle 7-8 digits: area code and outlet number. -The last 8-9 digits: customer account number. -Last bit: check digit (may be based on modulo 10 or a custom algorithm). -**Verification algorithm**: Some banks use custom weighted verification, but it is not fully disclosed. #### **2. United States** -**Routing Number (ABA)**: 9 digits, identifying banks and branches. -**Account Number**: The length is uncertain (usually 8-12 digits) and is allocated by the bank. -**Verification rules**: The Routing number must conform to the ABA verification algorithm (weighted summation modulo 10). #### **3. International Standard (IBAN)** -**Structure**: Country code (2 digits) + verification code (2 digits) + bank code (4 digits for the UK) + account information (up to 30 digits). -**Verification algorithm**: After converting IBAN to an integer, take modulo 97, and the result is 1, which is valid. --- ###**3. General verification algorithm** #### **1. Luhn algorithm** -**Purpose**: Widely used in credit card and some bank account verification. -**Steps**： 1. From right to left, even digits are multiplied by 2. 2. Add the digits of the product (e.g. 14→1+4=5). 3. The sum is added to the sum of odd digits. 4. If the result is a multiple of 10, it is valid. **Sample code (Python)**： ```python def luhn_checksum(number): digits = list(map(int, str(number))) odd = digits[-1::-2] even = digits[-2::-2] total = sum(odd) + sum(sum(divmod(d * 2, 10)) for d in even) return (10 - total % 10) % 10 ``` #### **2. Modulus algorithm (e.g. modulo 10, modulo 11)** -**Purpose**: Some banks customize verification (such as some account numbers in China). -**Method**: Modulo after weighting and summing a specific number of digits. --- ###**Fourth, the generation steps** 1. **Determine the rules of the target country/bank**: Consult relevant financial standard documents (such as ISO 13616-1 specification). 2. **Generate basic account number**: Combine bank code, branch code and customer serial number according to the rules. 3. **Calculate the check digit**: Use the corresponding algorithm (such as Luhn) to generate the last check digit. 4. **Verify uniqueness**: Make sure that the account number is not assigned repeatedly in the system. --- ###**Five, Precautions** -**Legal compliance**: Real account numbers need to be allocated by the bank, and self-generation is only for testing purposes. -**Data security**: Avoid using real account rules to generate sensitive data. -**Test data**: You can use a known test number (such as the US test Routing Number “021000022”). --- ###**6. Tool recommendation** -**IBAN Generator**: Online tool (如IBAN.com ). -**Development library**: Python's'schwifty` library can generate/verify IBAN. For detailed rules for specific countries/banks, it is recommended to consult the official documents of the local central bank or financial institution.