cann't find tax parameter in Wallet for digital goods

[Boris Os]

There is need to include tax in invoice. I can't find parameter in digital wallet docs https://developers.google.com/commerce/wallet/digital/docs/

But when buyer pays his invoice there is field "tax". 

Sample in your documentation https://developers.google.com/commerce/wallet/digital/docs/purchaseflow 

I need to know how I can include my own tax value instead of zero value?

[Alex Velichko]

I have the same problem with the "tax" filed.
Is there any ability in Google Wallet for Digital Goods to use taxes in payments?

[Boris Os]

Is there any administrator of the forum who can answer to me?