Research of 2,000 adults revealed 65% have struggled to understand terms and acronyms used in financial documents, with 36% of these claiming it has cost them £1,366.
Among the terms most likely to throw people off are APR (18%), compound interest (17%) and variable interest rate (14%).
Paying more for something or being overcharged (16%), having to pay interest or late fees (12%), or paying more tax than expected, were among the ways people have been caught out.
But this complex language could be leading to costly consequences for those living in the UK, who speak English as a second language, a separate poll of 500 revealed - with two-fifths regretting signing a financial agreement, compared to a third of native speakers.
And almost a quarter (23%) ended up paying more for something than they had previously expected, in contrast to the 16% of those born on the British Isles.
It also emerged 75% of those who have English as a second language are baffled by the slang used to describe money, compared to nearly half 45% of all Brits.
The research was commissioned by remittance provider Remitly Global, Inc, which has created "Quid's English" - an online glossary containing 25 confusing money phrases and slang terms to support anyone in the UK trying to navigate the nuances of money language.
The study also revealed the slang used across the country to describe money, with "dosh" most common in Bristol and "wad" popular in Newcastle.
A North/South divide emerged for certain phrases - with just 27% in London describing their cash as "readies", compared to 44% in Manchester.
While 33% in the capital have used the term "wonga" - rising to 46% in Newcastle.
Across the South East, 61% have "bucks" in their vocabulary, but just over half (52%) do in the North West.
Whereas "lolly" is prevalent in the South West, with 46% having used it in conversation, compared to 31% in the North East.
Generational differences also emerged - with Boomers and Gen X most likely to use "dough", "bucks", and "tuppence".
Whereas Millennials and Gen Z will use phrases like "Gs", "bags", and "cheddar" in comparison, the OnePoll.com research found.
Nine in 10 of Gen Z and 84% of Millennials either didn’t know the meaning or incorrectly guessed "bluey" is used to talk about £5, compared to 62% of Boomers.
How to shift your credit card debt quickly
By James Flanders, Consumer Reporter
UK Finance reports that we spend a whopping £2 billion a month using our credit cards.
While that little strip of plastic makes everyday spending easy peasy, it comes at a huge cost.
According to The Money Charity, the average credit card debt sits at £2,485 per household or £1,312 per adult.
And if you're stuck on a credit card with a high APR and only making the minimum repayments, you could be forking out hundreds of pounds extra in interest charges.
For example, if you owe £1,312 on your credit card and are charged 24.8% APR.
If you don't make any more transactions and pay £100 a month in repayments, you will pay off the card by September 2025 but at £207 in interest.
However, by hunting around for a better deal elsewhere and switching to a balance transfer credit card with a lengthy interest-free period, you can save yourself £162.
If the same person was accepted for a 28-month-long zero-interest credit card with a 3.4% balance transfer fee and made the same £100 repayments each month.
They would pay off the debt sooner, in July 2025, and only fork out £45 towards the 3.4% balance transfer fee.
Before taking out a new credit card or increasing the amount you borrow, it's vital to consider the consequences.
You should only borrow money if you can afford to pay it back.
It's always vital to ask yourself if you need to borrow before committing to a new credit card, personal loan or overdraft.
If you use a credit card, I'd recommend that you always pay off your balance in full at the end of each statement period.
Lenders have a responsibility to help customers who are in debt.
If you're in a debt crisis, your first point of call should be your lender.
They might help you out by offering you a reduced interest rate or a temporary payment holiday - so check in with your lender if you're struggling.
More than a fifth (21%) believe this general confusion comes from phrases from yesteryear still being used by older generations.
Danielle Treharne, for Remitly, said: “Moving to a new country presents unique challenges, especially when it involves navigating the complexities of new financial systems and learning new financial slang and terminology.
“The learning curve can be daunting, even costly, and it can often create barriers to accessing essential financial services.
“We’re constantly looking for ways to improve our customers' experience and to better understand their challenges.
“We believe in providing financial education and literacy resources that address common barriers - which is what inspired the launch of Quid's English.
“We hope this will help promote financial inclusion and individuals with cross border financial services needs.”
Credit card need-to-knows
Not using a credit card effectively can wreak havoc on your finances and your credit score.
If you don't keep up with repayments or default on your debt, you are likely to get a black mark on your credit record, which could affect your ability to get a credit card, loan or mortgage in the future.
It's important not to let yourself get sucked into overspending.
You should always clear the full balance as soon as possible.
If you have a poor credit score, don't bank on being approved for a card or getting the 0% deal you'd hoped for.
Card providers only have to give the advertised rate to 51% of applicants, so you could end up paying more interest than you bargained for.
If you've got a poor credit record, you're less likely to get the best rates.
And if you are looking for a new credit card, don't apply for lots at once.
After your 0% period is up, lenders can charge upwards of 40% interest, so if you have not repaid the debt fully by then, try to move the debt onto another 0% deal.
Top 10 confusing financial terms
1. APR - Annual Percentage Rate
2. Sub-prime lending
3. In perpetuity
4. Compound interest
5. Annuity
6. Progressive tax rates
7. Variable interest rate
8. Capital gain
9. Liquidity
10. Arrears
Top 10 slang phrases used to talk about money and finance
1. Skint
2. A rip-off
3. To make ends meet
4. Daylight robbery
5. Rainy day fund
6. Loaded
7. An arm and a leg
8. Bank of mum and dad
9. Quid’s in
10. Burning a hole in my pocket