One in five people didn’t cash in their £66 energy discount voucher in November, worrying new figures show.
The vouchers are being sent out as part of a £400 package of help over winter, split up over six months, to combat sky-high bills.
Those who pay by direct debit, on receipt of bill, or have a smart meter, should be receiving the money automatically.
But those with a traditional prepayment meter are sent vouchers, which they need to redeem the through PayPoint or a Post Office.
The vouchers typically only last 90 days after they were issued - and new data from PayPoint shows a concerning number of people missed this deadline.
Only 81% of those vouchers had been redeemed on Sunday when they ran out.
PayPoint said 79% of customers have so far redeemed their December vouchers. The rest have until March 8 to do so.
Meanwhile, the 28% of customers who have not yet redeemed their January vouchers have until April 9.
The vouchers are sent by post or through email or text message. Your energy supplier won't need to ask for your bank details to apply the discount - so be aware of scammers trying to contact you.
Steve O'Neill, corporate affairs and marketing director at PayPoint, said: "Last November's EBSS (energy bill support scheme) vouchers have now expired and overall redemptions are consistent with October vouchers at 81%.
"Our 28,000 retailer partners across the UK have once again done a fantastic job in supporting their local communities and delivering this vital support.
"Final redemptions of over four in five recipients is generally considered a good result for Government voucher schemes, based on others like the warm home discount."
He added: "A PayPoint survey of 2,000 adults using its services over the first three weeks of January showed 93% found it easy to redeem their EBSS vouchers at a top-up point.
"It also found 91% of people wait two weeks or less to redeem EBSS vouchers after receiving them, while 81% wait one week or less.
"Almost a quarter, 23%, said they wait less than a day."
Direct debit customers should be receiving their energy bill discount automatically - meaning you don't need to do anything to get the money off.
The cash will be applied either as a deduction to your monthly direct debit, or as a refund to your bank account after your direct debit has been taken.
If you don't pay by direct debit, the discount will be applied as a credit to your energy account each month.
The credit should appear as if you'd made a payment to your energy bill.
Smart prepayment meter customers will also receive the discount automatically each month.
