The £900 cash support for over eight million means-tested benefits claimants includes people on Universal Credit, Pension Credit and tax credits.
It will go directly to bank accounts in three payments, the DWP said.
More than six million people with disabilities will get an extra £150.
Separately, over eight million pensioners will receive an extra £300.
The three payments of up to £900 will vary depending on eligibility.
It follows the two payments totalling £650 which have already been made to more than eight million low-income households.
The first instalment of £326 was paid between 14 and 31 July. The second instalment of £324 should have reached those eligible by the end of December.
The payment reference on the recipients' bank accounts was their national insurance number, followed by "DWP COLP", as will be the case for the new payments.
Tax Credit-only customers who are not eligible for a payment from DWP will receive their payment from HMRC shortly after DWP payments begin.
The measures are part of government help towards assisting people with the soaring cost of living, which is rising at a near-record pace. It comes as the £400 energy bill help for all UK residents ends in April.
Work and Pensions Secretary Mel Stride said the cost-of-living payments would give a "financial boost" to the most vulnerable. However, charities and poverty campaigners have said the payments do not go far enough to mitigate the effects of increasing prices.
"The government has been recycling funding announcements and generally this amount just mops around the edges of what people are really facing," Stuart Bretherton from Fuel Poverty Action told the BBC.
"We want radical reform for energy pricing so that no-one falls below their minimal energy needs," he said.
In response, a spokesperson from the Department for Energy Security and Net Zero said: "We know this is a difficult time for families, which is why the government is covering around half of the typical household's energy bill".
The spokesperson added that improving energy efficiency in homes was the best long-term way of tackling fuel poverty.
It comes as a report found advances in the energy efficiency of UK homes were "negligible".
Meanwhile, Chancellor Jeremy Hunt said: "I know that times are tough, which is why a key focus of the Spring Budget was supporting people with the cost of living and helping people into well-paid work."