You are importing transactions into NetSuite SuiteTax from Amazon and are seeing duplicate tax/transactions in AvaTax.
- Enable 'Tax Details Override' setting found on the Items tab of invoice in NetSuite SuiteTax.
- This setting will stop any tax engine (e.g. Avalara, SuiteTax bundle, etc.) from calculating tax. Along with not calculating tax, the Tax Detail Override prevents the tax engine completely and thus will not post to AvaTax.