The Chancellor is reportedly considering a string of changes to the tax, which is typically charged at 40pc on assets above a £325,000 threshold when a person dies.
As well as increasing the headline rate or cutting the level at which the tax becomes payable, Ms Reeves could also alter reliefs and exemptions.
For example, the Treasury could amend a rule which allows money to be passed on tax free if it is given away at least seven years before someone dies.
It could also alter rules that exempt businesses and farmland from the tax.
The plans were first reported by the BBC. A Treasury spokesman told the corporation: "We do not comment on speculation around tax changes outside of fiscal events."
Any changes are likely to be highly controversial. Only 4pc of estates pay inheritance tax at present, but polling has consistently suggested the public regard it as unfair.
Jeremy Hunt, the shadow chancellor, has described it as "profoundly anti-Conservative".
Ms Reeves is understood to be planning the biggest tax raid in history in her Budget, which is to be held on October 30.
She has concluded there is a £40bn black hole in the public finances and intends to fill as much as 90pc of this gap with tax increases instead of cutting spending, after ruling out a return to Tory "austerity".