The quick answer
Prepare a CSV with the existing customers’ Internal IDs and only the fields to change. In Import CSV Records, choose Relationships, Customers Only, and Update. Verify the mappings, run the job, and inspect the same customer IDs afterward.
The screenshots use sample data and fictional person and operating-company names.
Before you start
Preserve Internal IDs from the account being updated. Category and Sales Rep must resolve to valid existing values; this example maps names and uses the standard Sales Rep field without Team Selling. Review blank-value behavior and workflow settings before a broader import. An omitted column and a mapped blank value are different. You need CSV import permission and access to Customer records.
01. Inspect the existing customers
Go to Lists → Relationships → Customers. Use a view with Internal ID, Category, Sales Rep, and Email. Confirm IDs 842 and 857 have blank values in these fields, rather than values hidden by the view. Export the customers’ Internal IDs to preserve those identities.
02. Review the prepared CSV
Read customer-updates.csv in a spreadsheet. ID 842 receives Wholesale, Morgan Reed, and billing@pinecrest.example. ID 857 receives Services, Morgan Reed, and accounts@harborfield.example. The four columns are Internal ID, Category, Sales Rep, and Email. This example reviews an already prepared file without editing it.
03. Choose the Update import
Open Setup → Import/Export → Import CSV Records. Choose Relationships, Customers Only, and Unicode (UTF-8), then select the same customer-updates.csv. Click Next and choose Update under Data Handling. Review Advanced Options and the customer form, then proceed to Field Mapping.
04. Check the field mappings
Map Internal ID to Customer: Internal ID, Category to Customer: Category, Sales Rep to Customer: Sales Rep, and Email to Customer: Email. Open the Category and Sales Rep mapping settings and confirm Reference Type is Name. Each name must resolve uniquely to a valid value in the account.
05. Run and check the import job
Click Next and choose Run from the Save & Run menu. Saving a reusable mapping is optional. Open Import Job Status and wait for completion. The example reports 2 of 2 records imported successfully. Inspect the CSV response if the job reports errors.
06. Verify the same customer IDs
Return to Customers and refresh the view. ID 842 should show Wholesale, Morgan Reed, and billing@pinecrest.example. ID 857 should show Services, Morgan Reed, and accounts@harborfield.example. Confirm the same identities remain and the test list still has two customers.
Check the result
- Internal IDs 842 and 857 still identify the original customers.
- All three target fields match the CSV on both records.
- The test list count remains two; broader workflow side effects need separate review.
Common questions
How do I update existing customers by CSV without creating duplicates?
Choose Relationships > Customers Only, upload the prepared file, and select Update under Data Handling. Map the CSV’s Internal ID to Customer: Internal ID. Preserve IDs exported from the same NetSuite account; do not use Add or Add or Update.
Which field identifies the existing customer during the import?
Use the system-generated Internal ID, such as 842 or 857, mapped to Customer: Internal ID. Internal IDs are account-specific and should come from the account being updated. Customer names or business identifiers may not reliably identify the intended record.
How should Category and Sales Rep references be mapped?
Map Category to Customer: Category and Sales Rep to Customer: Sales Rep. In this example, use reference type Name and confirm values resolve uniquely. Available fields, reference choices, and Sales Rep behavior depend on account configuration, subsidiary eligibility, and Team Selling settings.
Why verify customer records after the import says Complete?
A completed job confirms processing status, not necessarily that every intended value is correct. Refresh the customer view, confirm Internal IDs 842 and 857 still identify the same customers, inspect Category, Sales Rep, and Email, and confirm the test count remains unchanged.