Advanced Numbering is a hidden feature. You must request to have the preference unhidden in your account to enable it.
To enable the Advanced Numbering feature:
1. Contact NetSuite Customer Support and request the feature.
Note: We recommend you test Advanced Numbering in a sandbox account before you enable it in your production account.
2. Go to Setup > Company > Enable Features (Administrator). In the Company subtab, scroll to the ERP General subsection and check the Advanced Numbering box.
3. Click Save