I just confirmed with the ATO that the CC surcharge when paying tax by CC is tax deductable.
The surcharge is a cost associated with paying tax and is therefore claimable under D9.
Now that the 3x miles for Platinum Amex has expired, the 0.65% surcharge for Visa is more attractive than the 1.25% surcharge for Amex.
By my calculations, a European round trip in business booked via online redemption is 255,000 miles.
With Platinum Visa, that is $255,000 tax paid.
Surcharge on that is $1,657.50
Tax deduction in top tax bracket means you will actually pay 53.5% ($886.76)
Add the Airport/Govt taxes ($223.80)
Plus Carrier Surcharges ($458.80)
Grand total is $1,570 cost for an approx $9k ticket.
Not bad.
Obviously most will not pay $255,000 tax in one year, but on a pro-rata basis, you would earn the equivalent amount of miles if you have a taxable income of >$180K/year.