Millions of Brits are sleepwalking into expensive estate planning blunders that could leave them facing hefty tax bills and financial headaches - these are the most common, according to experts. Financial advisers say among the biggest misconceptions is the belief that estate planning only matters for the wealthy or elderly, when in reality almost anyone with property, savings, pensions or children should be considering it far sooner.

A widespread issue is that numerous people either never create a will at all or neglect to update one following major life changes such as marriage, divorce, having children or purchasing property. Many also lack a Lasting Power of Attorney, a £92 document that sets out how you want your affairs to be handled should you no longer be capable of doing so due to ill health, for instance.

Others mistakenly assume their assets will automatically transfer to their intended beneficiaries, only for loved ones to uncover complicated legal problems after death. Experts also caution that forthcoming inheritance tax (IHT) changes from April 2027, when pensions are anticipated to become part of estates for IHT purposes, could make inadequate planning considerably more costly for families in the coming years.

Perhaps most worryingly, advisers report that the overwhelming majority of individuals simply sidestep the subject entirely because it feels awkward, complex or something that can perpetually be postponed. However, according to financial planners and estate specialists, postponing crucial decisions surrounding wills, powers of attorney, pensions and gifting strategies can leave families confronting severe emotional and financial repercussions at precisely the most difficult moment.

Rebecca Robertson, Independent Financial Adviser, planner and director of Evolution Financial Planning, said people made a series of assumptions about what would happen with their assets if they died.

She added: "The two most common mistakes I see are married couples assuming all assets go to each other and non-married couples not considering what will happen without a will, which can be a major issue for women without any personal assets. The majority of people like to hope for the best and, only when they have to deal with a family's estate when someone has passed away, do they realise the complexity of it all. One milestone when people do recognise they need a will is when they have children, but this is generally at a time when finances are straightforward.

"Often over time the will becomes old and out of date. Again only years later when they are dealing with another family member or they come across an issue, will they act. If they haven't, they have missed an opportunity. This is going to be even more important post-April 2027, when pensions become part of the estate."

Steven Greenall, director of Greenall Estate Planning, stressed that drawing up a will was absolutely vital.

He added: "Everyone knows they need a will and a Lasting Power of Attorney, but they keep putting them off until it's too late. Trying to cut corners and preparing a will without seeking advice or transferring property while the testator is still alive, without considering the seven-year rule or gifts with reservation of benefits, can really cause a lot of unintended consequences. Not updating wills after life events such as divorce or remarriage often sees inheritance going to people it's no longer intended for."

Nouran Moustafa, practice principal and IFA at Roxton Wealth, revealed that in her experience, only 10% to 15% of people were adequately prepared.

She added: "The biggest mistake is thinking estate planning is only for the very wealthy or very old. It is not. It is about control, protection and making sure the people you love are not left with a legal and financial mess. In practice, I see people delay writing a will, forget to update it after marriage, divorce, children or buying property, and assume assets will automatically go where they want.

"Pension nominations are often outdated or missing, which is a huge blind spot. Power of attorney is another area people ignore. Everyone thinks about death, but very few plan for incapacity, even though that can cause immediate problems with bills, property and family decisions. In my experience, only around 10-15% of people have all their ducks in a row.

"Most have fragments: maybe an old will, no LPA, pension nominations they cannot remember, and no joined-up plan. People avoid it because it feels uncomfortable and complicated. But estate planning is not morbid; it is an act of care."

Antonia Medlicott, founder and MD of London-based Investing Insiders, emphasised the importance of keeping wills current.

She added: "One major error that people make with estate planning is only doing it once and then leaving it stored away for years to come. A lot will happen over time as lives change, including new family members being born and rule changes, so, while this may be uncomfortable, it needs to be done more regularly to ensure your wishes are followed.

"Research reveals that 11% of UK adults with a will admitted that it no longer reflected their current wishes, and the average time since last updating their will was six years. A key mistake is waiting too long to gift, which can leave a financial burden on loved ones.

"If death occurs before seven years pass, then the beneficiaries will be left with a tax bill under current IHT rules, although taper relief can reduce the tax rate after a certain period of time. Impending changes that bring pensions into IHT in 2027 make this worse and mean that millions of families will need to evaluate and change their planning strategy."

Rob Mansfield, Independent Financial Advisor at Tonbridge-based Rootes Wealth Management, warned that attempting to circumvent the system with IHT simply would not work.

He added: "Not knowing the rules is the first one. There are so many misconceptions flying about and it's not the easiest tax to understand.

"A really common mistake is thinking that you can place your house in your kids' names, and trick the system. It doesn't work and it can be really time-consuming and expensive to unpick."

Graham Nicoll, financial planner, Chartered FCSI at NCL Wealth Partners, stressed that getting ahead of the game early was crucial to avoiding costly errors.

He added: "One of the biggest estate planning mistakes is failing to put the right legal foundations in place. Many people still do not have a Lasting Power of Attorney, which can leave loved ones unable to manage affairs if capacity is lost. Another common issue is not having an updated will.

"As family circumstances, assets and wishes change, wills should evolve too, otherwise important decisions are left to chance. The biggest mistake, however, is treating estate planning as a single issue, whether that is gifting assets or using insurance to fund an IHT bill.

"Effective planning should be holistic, balancing lifetime objectives, family wishes, tax efficiency and succession planning. For larger estates, the best outcomes are often achieved through collaboration between a financial planner and a private client solicitor or accountant. Early planning and professional advice are key."

Riz Malik, Independent Financial Adviser at Southend-on-Sea-based R3 Wealth, urged individuals to consult a qualified professional when navigating estate planning.

He added: "Many mistakes people make when estate planning come from them trying to do it themselves rather than seeking professional advice. One mistake that people make is trying to transfer their assets or make gifts to their loved ones without fully considering the implications. If you want your wealth to remain within your family, consider that it could be diluted by your current or future son or daughter-in-law's next partner."