A mortgage expert has issued a warning to anyone buying a home this year. He is urging people to avoid a simple paperwork mistake that could cost them thousands of pounds.

David Sampson, a mortgage expert at HMO Mortgage Broker, says house buyers often reveal more financial information than is necessary to estate agents. Although most buyers believe that showing the maximum number they can borrow strengthens their position, Mr Sampson explained that it often works against them. He said: “If your decision in principle shows that you can borrow £300,000 and you have a £30,000 deposit, then the estate agent right away can see that you are capable of paying £330,000. If you then put a cheeky offer in of £290,000, you’ve already shown that there is wiggle room in your offer.”

“You need to remember, estate agents don’t work for you, they work for the seller, and once they know there is headroom, they are far more likely to encourage counter offers or push the buyer closer to the asking price.”

According to Mr Sampson, this mistake is common because buyers are often keen to appear credible when purchasing a home. He stressed that reducing the number will not weaken your offer.

Mr Sampson explained: “Being smart with your decision in principle can minimise the chance of the seller adding small increases that soon add up during negotiations, all because the agent knows the buyer can afford it. In competitive areas, it’s easy for those negotiations to add a further £10,000 without the buyer realising what has happened.”

He also recommended requesting a version that matches the offer price exactly rather than submitting a decision in principle showing the maximum affordability. People often avoid doing this as they think it takes them a long time or weakens their offer.

Mr Sampson said: “For example, if you are offering £290,000 and you have a £30,000 deposit, your decision in principle should show borrowing of £260,000. This way, your paperwork supports your offer rather than undermining it.”

He added: “There’s no penalty for this as lenders expect decisions in principle to change as buyers adjust their budgets, so make sure to make the most out of this to your advantage.”

“This isn’t dishonest, you aren’t hiding funds or lying about anything. You simply aren’t oversharing, so you aren’t taken advantage of. In competitive areas, this could save you upwards of £10,000, in others, it could save you anywhere from £2000 to £5000. This money can cover solicitor fees, surveys or even moving costs