The Prime Minister has indicated she will ditch the Tory pledge not to raise taxes but promised not to increase VAT.
Theresa May said the Conservatives had no plans to raise taxes, but did not want to make specific proposals unless she was sure she could deliver on them.
However, she did promise there would be no hike in VAT, leaving a question mark over income tax and national insurance.
Mrs May also signalled she would scrap the triple lock protecting pensions, which has been another promise made by her predecessor David Cameron in 2015.
Chancellor Philip Hammond has already paved the way for the measures to be ditched arguing that previously made commitments "constrain" the Government.
The tax lock promise recently caused problems for Mr Hammond when he was forced to climbdown over planned national insurance changes for the self-employed in the face of a Conservative backbench revolt.
The PM told ITV's Peston on Sunday: "We have no plans to raise the level of tax.
"In relation to specific taxes, we won't be increasing VAT."
Speaking on BBC One's Andrew Marr Show, Mrs May said she intended to cut taxes "on working families" if the Tories were returned to power on 8 June.
She said: "We have absolutely no plans to increase the level of tax but I'm also very clear that we don't want to make specific proposals on taxes unless I'm absolutely sure that I can deliver on those.
"But it would be my intention as a Conservative government and as a Conservative prime minister to reduce the taxes on working families.
"And if you've got strong and stable leadership that's absolutely what you can do."
Mrs May also hinted she would scrap the pensions triple lock, but promised the state payouts would continue to rise.
The current measure ensures the state pension increases in line with wages, inflation or by 2.5%, whichever is highest.
There have been growing calls to ditch the policy because of concerns over cost.
The PM said: "Under a Conservative government the state pension will still go up every year of the next parliament.
"Exactly how we calculate that increase will be for the manifesto, and as I have just said you will have to wait for the manifesto to see what's in it."
Mrs May's comments on taxes have been seized on by Labour.
Shadow foreign secretary Emily Thornberry told Sky News' Sophy Ridge on Sunday programme: "She's saying she has no plans to raise income tax on middle incomes and lower incomes, now that to us is code.
"That is the code the Tories used before the first time they came in when they then went ahead and increased VAT.
"So she has ruled out increasing VAT, but she is not ruling out raising taxes for lower and middle income people."
However, Ms Thornberry refused to be drawn on what Labour's policy on taxes would be and said people would have to wait until the publication of the party's manifesto.