The government is planning to increase the amount of money it raises in inheritance tax at the Budget, the BBC has learned.
It is not known how many people are likely to end up paying more, nor how much more they would pay.
It is understood the prime minister and the chancellor are considering multiple changes to the tax, which currently includes several exemptions and reliefs.
Inheritance tax is charged at 40% on the property, possessions and money of somebody who has died above the £325,000 threshold.
It raises about £7bn a year for the government.
Around 4% of deaths result in an inheritance tax charge.
The tax includes a series of exemptions which over the years several governments have considered changing in order to raise more money.
It is thought changes to a number of these are under consideration.
Current exemptions and reliefs include rules around gifts that are given while you are alive.
If a person gives away more than £325,000 in cash or gifts but dies within seven years, recipients could be liable to pay inheritance tax.
There is also Business Relief for Inheritance Tax, and Agricultural Relief, which allows land or pasture that is used to grow crops or to rear animals to be free of Inheritance Tax.
It is not known what changes will be made in the Budget on Wednesday, 30 October.
A spokesman for the Treasury told the BBC: “We do not comment on speculation around tax changes outside of fiscal events.”
Ministers are attempting to plug what they claim is a £40bn shortfall between what they want to spend and the amount of tax they expect to collect.
Government sources say it is vital there is a “reset in the public finances” and are keen to emphasise what they see as the “scale of the challenge”.
This can be seen as part of the expectation management ahead of Rachel Reeves’ address.
Most new governments put up taxes immediately after a general election.
The Budget is expected to be billed as “Fixing the Foundations to Deliver Change”.
Both the prime minister and the chancellor have already appeared in front of lecterns branded “Fixing the Foundations” – an attempt to highlight what they claim is the mess they inherited from the Conservatives.
For several weeks, senior government figures have been strongly hinting that there will be increases to the amount of National Insurance paid by employers.
The Labour manifesto before the general election said that “Labour will not increase taxes on working people, which is why we will not increase National Insurance, the basic, higher, or additional rates of Income Tax, or VAT”.
This massively limits their options to raise more tax revenue.
But ministers appear willing to stretch the spirit if not the letter of their promise by putting up National Insurance on employers, some of whom – smaller businesses – would probably regard themselves as working people.
The chancellor is expected to give herself extra breathing space by changing the government’s self imposed rules on when it can borrow money, and has told some government departments that their budgets will be lower than they want.
A Labour source said that the negotiations on spending had provoked “significant angst” across the cabinet.
Shadow Chancellor Jeremy Hunt told the BBC: “During the election we repeatedly warned that Labour’s sums didn’t add up and that they were planning to raise taxes. The real scandal is that despite planning these tax rises all along, they didn’t have the courage to admit it to the public during the election campaign.
“Unfortunately, it looks like it will be people who have saved all their life to provide an inheritance to their family who will pay the price for Labour’s tax rises.”
Source: BBC World