Paying your personal Income Tax is not a commercial transaction. Just like paying fine, traffic challan, toll taxes are not commercial transaction.
The banks and government itself encourages paying of Income Tax using Credit Card.
I have seen banks discouraging users to pay commercial electricity bills using personal credit card. The specifically mention this in their T&Cs. But, I haven't seen any bank warning its users for paying Income Tax with Credit Card.
Paying income tax through credit card is quick and hassle-free with benefits. But read to know whether it is worth paying your tax online using a credit card.
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