What causes this error when saving a customer record?

(400)[USER_ERROR]Illegal ID. Please enter a name.

AI generated answer (using internal Slack threads):

The error

(400)[USER_ERROR]Illegal ID. Please enter a name.

is typically caused when you are trying to save a customer record with an ID that already exists in the system or when the ID field is left blank. In NetSuite, the ID field is a unique identifier for each record, and it cannot be duplicated or left empty. When creating a customer record via SuiteScript, unlike the UI, the system does not automatically append a number to the customer's name (ID) when it finds a duplicate entry. You have to manually handle this in SuiteScript. One way to handle this is to perform a search before creating the customer record. If the name already exists, you can append a unique identifier (like a number or part of a transaction ID) to the name to ensure it is unique. Another approach is to enable auto-numbering for customer records. However, this might result in seeing generic IDs like 'Cust 00123' in the UI, which might not be ideal for your use case. Remember, the ID field is crucial for record identification in NetSuite, so it's important to ensure it is unique and not left empty when creating or updating records. ****** Disclaimer: This response was generated by an artificial intelligence assistant based on previous conversations from multiple Slack channels, and may contain inaccuracies or mistakes. ******