Millions of eligible Scots have yet to claim £400 worth of help with their bills with just 30 days left to do so.
Households with traditional prepayment meters have been urged to avoid missing out on the energy support vouchers, with £130m still available to be claimed across the UK.
The Claim Your Energy Voucher Day is a final push to encourage the remaining households to claim their vouchers before the scheme ends in a month.
All households were eligible for the Government’s Energy Bills Support Scheme, which paid £400 in six instalments of £66 or £67 over the winter.
However prepayment customers – often some of the most vulnerable – were paid in vouchers and millions remain unclaimed.
Some customers did not receive them, while others have struggled to redeem them.
Customers need to visit a post office or PayPoint with their Energy Bills Support vouchers and identification before June 30.
Any lost, missing or expired vouchers can be reissued, as long as they are redeemed by June 30.
Those on a traditional prepayment meter who have not received the vouchers, or are unsure of how to redeem them, or need a voucher to be reissued, should contact their supplier.
Latest figures show the number of vouchers cashed in has reached an all-time high of 83%, with prepayment meter users so far claiming nearly £650m under the scheme.
The figures, published earlier this month, show that around 25% of vouchers in Scotland are yet to be claimed.
Adam Scorer, chief executive at National Energy Action, said: “We urge anyone who hasn’t yet claimed their vouchers to do so before the June 30 deadline and if you have friends and family that may not have used their vouchers, spread the word.
“It may be the support that keeps their lights on, their oven cooking, their hot showers running, through the summer. It’s vital money at a time when it’s never been needed more.”
Energy minister Amanda Solloway said the Government was making “huge strides” in getting nearly £650m from the Energy Bills Support Scheme out to prepayment meter customers.
“Tell friends and family or anyone on a traditional prepayment meter to use their vouchers for up to £400 off bills before June 30 – there is still £130m out there to claim,” she said.
Matthew Cole, head of Fuel Bank Foundation, the national charity that provides emergency fuel vouchers to prepayment meter customers, said: “We’re really concerned that hundreds of thousands of people with traditional prepayment meters are going to miss out on this vital financial support.
“As part of our own campaigning on this issue, we found that other reasons why vouchers haven’t been redeemed included not receiving them, due to incorrect details or the person having moved house and their records haven’t been updated, or they lost or deleted the voucher.
“However, whatever the reason, we want to reassure people that if they haven’t claimed their voucher, there is still time to do so.”
Households using prepayment meters who use alternative fuels such as LPG, heating oil or biomass as the main way they heat their homes also have until June 30 to use their vouchers worth up to £200 in energy bills support.
Customers will have received these vouchers in the post from their supplier and should contact them if they have any questions.