You can change how NetSuite searches for duplicates on the Duplicate Detection page. You can have NetSuite search for duplicates among customer, contact, partner, or vendor records and search for matching information in certain fields.
To prevent you from merging records that are not duplicates, you can only merge records if they have the same tax registration number or if both records do not have tax registration numbers entered.
To set up Duplicate Detection:
Go to Setup > Company > Duplicate Detection.
Check the box next to each type of record you'd like use duplicate detection with.
For example, check the Detect Customer Duplicates box to be alerted of possible duplicate Customer records.
There are four types of records you can detect duplicates for:
For each type of record, in the Fields to Match On box, select the fields from respective record type you want to use when searching for similar information.
Depending on your settings in Home > Set Preferences, you may see all fields listed in the form or you may have to click the Select Multiple icon, and select your fields from there.
For a record of type Customer, selecting the field Company Name, makes the system search for duplicate matches in the Company Name field in the Customer Form.
Records must have matching information in all of the fields you select to be returned as possible duplicates.
For example, if you check the Detect Customer Duplicated box and then select phone and email in the Fields to Match On field, customers must have a matching phone number and a matching email address to be considered duplicates.