Perhaps I'm missing something here as you haven't given a heap...

Perhaps I'm missing something here as you haven't given a heap of information but I wouldn't have thought there'd be any tax deductions available under these circumstances.

Repurchase of BRN shares post-discharge of mortgage would simply be the purchase of shares on capital account so there'd be no deduction and you'd be subject to CGT provisions similarly to your originally owned shares prior to the discharge of your mortgage.

The interest on the loan used to repurchase the BRN shares would only be tax-deductible if BRN were paying dividends hence creating a nexus between the interest expense and assessable income.

The only circumstance in which I see a deduction being available is if you were to be share trading such that your repurchase of BRN shares is on revenue account and so any loss at year-end would be tax deductible, but that in itself would be a poor result as you'd have lost money on your trades and so would be a fruitless excercise.

If I've missed something I'd be interested to know!

Cheers FF

All IMO of course.