Standard Tax Codes, EC Code and International Tax Codes in Transactions

Check first these settings:

1) Navigate to Setup > Accounting > Setup Taxes > Enable Tax Lookup on Sales Transactions = T
International Tax Code = e.g. O-GB
2) Item record's Tax Code = SR-GB
3) Navigate to Setup > Accounting > Tax Codes:

*SR-GB(20%)
Tax Rate = 20%
*EG-GB
Tax Rate = 0%
EC Code = T
Notional Rate Derived from = SR-GB(20%)
*O-GB
Tax Rate = 0%
Export = T

Note: Tax Code names may vary for different Customers. What is important is each tax code's properties are setup correctly.

4) Customer/Vendor has Shipping Address (UK or any of EU Member States)
5) Customer/Vendor has Tax ID
- List > Relationships > Customer or Vendor > Financial Tab

NetSuite automatically pulls up the following tax codes in transactions when Customer/Vendor's Shipping Country and Tax ID are:

Tax Code Shipping Country Tax ID
SR - GB - in UK not empty/empty
SR - GB - in any of EU Member States empty
EG - GB - in any of EU Member States not empty
O-GB - outside UK/ EU Member States empty