UK households have been warned that they could be landed with a £100 fine if they are not careful. There has been a significant drop in the earnings threshold between universal credit and tax credits, leading to a dramatic surge in people being fined. Under credits, households earning up to around £14,520 a year after tax could still qualify for free NHS prescriptions and dental treatment.

But, under universal credit, that figure falls to roughly £5,220 or £11,220 depending on one’s circumstances, according to MoneySavingExpert. For many people, that gap alone is enough to strip away entitlements they assumed were still in place. Tax credits are also assessed once a year, but universal credit is done monthly, meaning entitlement can shift depending on what a person earns in a given assessment period.

Finance expert Martin Lewis said: “Many who were on tax credits, they get to the box at the dentist, or they get to prescriptions, and they just tick the tax credits, jobseeker’s allowance or universal credit boxes.

“Then they get sent a letter saying, can you check that you’re really eligible, because they don’t realise the income threshold is different.

“They don’t do that, and then there’s up to £100 fine for those people that they don’t realise they’re doing anything wrong.”

A spokesperson for dental experts Forever Dental and Skin said: “Dental treatment can already be costly, so being caught off guard by a fine on top of that is the last thing anyone needs.

“Before your next dental appointment, it is worth taking a few minutes to check whether your move to Universal Credit has affected your eligibility for free treatment.

“The criteria are different from what they were under Tax Credits, and many people simply will not be aware of that yet.

“A little caution goes a long way when it comes to medical costs — and in this case, a quick check could save you from an unexpected £100 fine arriving in the post.”