Nicola Sturgeon will promise the basic rate of income tax will not be increased in Scotland if she is returned as First Minister.
The SNP leader will make the pledge when she addresses her party's spring conference in Glasgow on Saturday afternoon.
She will also announce plans for free lunches, which are already given to youngsters in the first three years of primary school, to be expanded into nurseries when childcare provision is increased.
The conference comes less than two months before the next Holyrood elections and at time when the SNP is riding high in opinion polls, which put the party on track to win a second majority term.
While both Scottish Labour and the Scottish Liberal Democrats have called for an immediate 1p increase in the basic rate of income tax to help fund local services and education, Ms Sturgeon will insist: "Taxing the lowest-paid doesn't tackle austerity, it simply passes the burden of Tory austerity to the shoulders of those who can least afford it and that is not fair.
"I think it would be wrong at this time to raise taxes on the lower-paid."
While the SNP "are determined to make this country fairer", the First Minister will also stress the need for the country to be "an attractive place to live, work and do business".
More details on how the party would use the new income tax powers coming to Holyrood will be revealed after the UK Budget but Ms Sturgeon will use her speech to set out some "key principles".
She will tell voters in Scotland: "Firstly, we will never forget that every decision we take on tax has to be paid for by you, the hard-working people of this country.
"Secondly, we will not raise the basic rate of income tax in the next parliament.
"I don't think there's anything left-wing about a competition over who can tax ordinary people the most."
She will also argue that given the UK's economic circumstances, any tax cuts to the better-off by George Osborne would be "deeply wrong".
Ms Sturgeon will say: "We will not do that - our choice will be to invest more in our public services instead."
Decisions over tax will be "reasonable and balanced", the First Minister will add, promising: "They will be fair to all taxpayers, they will be fair to our economy and they will be fair to our public services. Because that is what you have a right to expect from your party of government."
The SNP has already pledged to increase the amount of free childcare three and four-year-olds, and some vulnerable two-year-olds, are entitled to if it wins the Holyrood election, raising this from 16 hours a week to 30 over the course of the next parliament.
The First Minister's speech will set out an additional commitment on the provision of free meals for these youngsters.
"In the last parliament, we delivered free school meals for all children in primary 1-3, benefiting 135,000 children and saving families £380 a year for each child," she will say.
"Today I can announce, that when we expand early-years education to include full-day provision, we will extend entitlement to free meals to our nurseries too.
"Making sure that our youngest children get access to a healthy nutritious meal that improves their capacity to learn, without the stigma of means testing."
A spokesman for the Scottish Conservatives said: "Our pledge at this election is simply that people here should not have to pay higher taxes than those elsewhere in the UK.
"The SNP, Labour and the Lib Dems need to end their bidding war on higher taxes and instead think about a plan that supports Scottish jobs and grows our economy."
Scottish Labour said that, with new tax powers coming to Holyrood, "there are no more excuses for accepting cuts to schools and services".
The party's spokesman for opportunity Iain Gray said: "If Nicola Sturgeon doesn't grasp this opportunity to be bold now, she never will.
"The most important investment we can make in the future of our economy is in education, but instead the SNP government have slashed education and training spending by 10% since they came to office in 2007.
"The First Minister said education would be the driving and defining priority of her government. Today she has the chance to prove it."
Scottish Liberal Democrat leader Willie Rennie said: "At her conference Nicola Sturgeon has the chance to put independence speculation to bed and focus on getting Scotland fit for the future using the powers that we already have. That starts with education.
"There is so much we can do right now to help children, support families and get our education system back on track. That needs to be the First Minister's focus, not keeping the independence fires burning."