In his keynote speech to the Labour conference, the Shadow Chancellor will say he needs to be "straight" with the public about the need for tough choices, making it clear a Labour government would initially stick with the Coalition's tight spending limits and would also have to make cuts to balance the books.
"In tough times it's even more important all our policies and commitments are properly costed and funded. The British people rightly want to know the sums add up. So we will go one step further and ask the Office for Budget Responsibility to independently audit the costings of every individual spending and tax measure in Labour's manifesto at the next election," he will say.
Mr Balls will add: "This is the first time a Shadow Chancellor - the first time any political party in Britain - has ever said it wants this kind of independent audit. A radical change from what's gone before, but the right thing to do to help restore trust in politics."
His bid to convince the nation Labour can exercise "iron discipline" in office comes after Johann Lamont, in her conference address, launched a withering attack on the SNP, branding nationalism deceitful and divisive and saying the prize at the 2014 referendum was to "defeat the politics of nationalism ... a virus that has affected so many nations and done so much harm; an ideology that never achieved anything".
The SNP hit back, dismissing the Scottish Labour leader's comments as "ignorant, offensive and distasteful", and completely at odds with the No campaign's professed desire for a positive debate, free from abuse.
As Labour trail behind the Conservatives by 18 points on the issue of economic competence, the leadership is aware it needs to underline its fiscal credibility. Yesterday, it was faced with a Coalition charge of a £28 billion black hole in Labour proposals - more than £1000 for every household - which Ed Miliband dismissed as "nonsense". He made it clear any Labour pledge would be "properly costed and clearly funded".
The party leader insisted Labour had detailed policies on bread-and-butter issues such as pledging to scrap the bedroom tax, "strengthening" the minimum wage and curtailing immigration. Asked about his party's poll ratings, Mr Miliband said: "Polls go up and down; what goes up and up is the cost of living."
In his address today, Mr Balls will attack the Coalition's record of three years of a flatlining economy and say while the figures are improving, "for millions of families this is no recovery at all". The Shadow Chancellor will be clear that, if Labour wins power in 2015, austerity would continue with no more borrowing for day-to-day spending and tough fiscal rules to balance the current budget and get the national debt down.
Yet he will stress Labour will always make different choices from the Tories.
"We will combine iron discipline on spending control with a fairer approach to deficit reduction, but we won't be able to reverse all the spending cuts and tax rises the Tories have pushed through. And we will have to govern with less money. The next Labour government will have to make cuts too because while jobs and growth are vital to getting the deficit down - something this Government has never understood - they cannot magic the whole deficit away at a stroke."
The Shadow Chancellor will add: "Delivering our Labour goals will be harder than at any time in living memory. But it can be done if we get people back to work and strengthen our economy, cut out waste and focus relentlessly on our priorities, and make sure difficult choices are rooted in fairness and in common sense."
Elsewhere at conference today, a call will be made for the party to end the public-sector pay cap to help support growth, improve services and tackle the cost-of-living crisis.