The 1956 tax treaty between the UK and India means that someone domiciled in India, like Rishi Sunak's wife, Akshata Murty, is never subject to UK inheritance tax on their non-UK situs property, no matter how long they live in the UK.

Dan Neidle founder Tax Policy Associates highlighted this in a LinkedIn post on 28 September arguing "lots of people [are] saying Rishi Sunak's family would get a £300m benefit from the abolition of inheritance tax. They're wrong. The Sunaks are already mostly exempt, thanks to an obscure 1950s loophole."

But he further said in an article that "the handful of treaties that work this way should be amended or repealed, and the loophole closed".

He said Murty, is worth at least £750m. On the face of it, their family would stand to gain by £300m if inheritance tax was abolished. However Murty likely is an accidental beneficiary of an obscure loophole, which means her wealth will always be exempt from inheritance tax.

If a UK domiciled individual held £750m of shares then, when they and their spouse died, their estate would usually have an inheritance tax bill of around £300m.

"There was a fuss last year about Akshata Murty being a "non-dom" - meaning that she was born abroad and (broadly speaking) regards her permanent long-term home as being in India, not the UK. This enabled Ms Murty to historically claim the "remittance basis", which means she wasn't taxed in the UK on her Infosys dividends. However she agreed last year to stop claiming the remittance basis.

"You have to actively claim the remittance basis by ticking a box on a tax return, but being a non-dom is not a choice - it's a matter of law. So it's likely Ms Murty remains a non-dom. That means Ms Murty's estate wouldn't be subject to inheritance tax on her Indian shares.

"That is a very beneficial result for non-doms and their families but, since the 2017 reforms, it runs out after the non-dom has (broadly speaking) been living in the UK for 15 years. That probably gives Ms Murty around four more years before her estate becomes taxable."