It's an old tax question: if I borrow to pay a tax bill do I get a deduction for the interest on the loan? The ATO view has always been (since about 1930 at least) that the interest is deductible for companies and self-employed because paying tax is a cost of running a business and the interest incurred to borrow to pay a business cost is deductible, see:
ATO ID 2006/269 - Deductions and Expenses: interest incurred on moneys borrowed by a sole trader to pay income tax
However the ATO does
not allow deductions for employees in the same circumstance. The ATO view is that tax employees pay is a deduction from their income after the income earning process has finished. Since its not a cost of earning income interest on borrowings to pay it is not deductible.
I discussed this back in post 204 in this thread and explained why I think by analogy the credit card fee should be deductible to companies and the self-employed, namely, the CC fee is a cost of paying your tax in the same way incurring interest on a borrowing to pay your tax is.
The best advice is to ask your accountant. That way even if the ATO changes its mind about this you will have the protection of having sought advice.