Indicates how the merchant is handling taxes
Valid values:
0 - NLL (net prices with tax calculated a line item level)
1 - NIL (net prices with tax calculated at invoice level)
2 - GLL (gross prices given with tax information provided at the line item level)
3 - GIL (gross prices given with tax information provided at invoice level)
4 - NON (no tax applies on the invoice for the transaction)