Around seven million UK adults with £10,000 or more in cash savings could be missing out on higher long-term returns because they are not investing, according to the Financial Conduct Authority (FCA). Fewer than one in 10 people have received regulated financial advice on pensions or investments in the last year, leaving many unsure whether to leave money in the bank or put it to work elsewhere.The idea that you should build a £10,000 cash pot before investing can be a useful milestone, but it’s not a universal rule.What matters far more is what the money is for and when you are likely to need it.What should stay in cash?Dan Coatsworth, head of markets at AJ Bell, says: “Investing is generally only suitable for money that you don’t plan to spend for five years or more. Make sure you’ve got three to six months’ essential living expenses in cash for emergencies, as well as any money you’ll need in the next five years - for a big holiday, or a new car, for example.“Any savings goal that’s further out than five years could be ideal for investing. It’s also important to pay off any expensive debt such as high APR credit cards or personal loans before you invest.”That means someone with £15,000 saved is not automatically ready to invest, while someone with £6,000 could be - if they have a secure income, lower outgoings and no major spending plans or debt.Rather than aiming for a fixed savings target, many experts suggest thinking in layers.First, comes an emergency fund.Next, any known spending over the next few years.Only after those are covered should long-term money be considered for investing.Some people may also choose to start investing gradually, rather than waiting until they have reached a fixed savings figure. Drip-feeding a set amount each month can feel less daunting than moving a lump sum in one go, while still allowing them to keep building their cash buffer.When does cash become a missed opportunity?Over longer periods, inflation steadily erodes its spending power and savings rates change. For money that won’t be touched for years, leaving everything in cash can become a huge missed opportunity.(Getty Images)Get a free fractional share worth up to £100.Capital at risk.Terms and conditions apply.Go to websiteADVERTISEMENTGet a free fractional share worth up to £100.Capital at risk.Terms and conditions apply.Go to websiteADVERTISEMENTCoatsworth says: “Many people treat large cash sums as a safety net - a ‘just in case’ pot that ensures they can deal with any unforeseen financial needs. It’s important to have an emergency pot, but holding excessive sums is a wasted opportunity to put some of that money to work elsewhere.“In addition, a large pot of cash creates temptation to keep dipping in and spending some of that money.”The FCA's own research reflects that caution. It found that almost two-thirds (61 per cent) of adults with more than £10,000 in investible assets keep at least three quarters of that in cash rather than investments.What help is available?The FCA is developing a new system of “targeted support”, intended to help firms give more personalised guidance to customers who are not receiving full financial advice. “Investing for the first time can feel daunting, but don’t let that put you off,” Coatsworth says.“Funds can be an easier place to start than buying individual company shares. It’s like buying an assorted box of biscuits - inside, you get lots of different flavours. If something goes wrong with one of the holdings inside the fund, you’ve hopefully got all the other holdings to act as a cushion to minimise the impact.”He also notes that professionals can choose your allocation if you have no knowledge or interest in choosing countries, sectors or companies, while many platforms have automatically diversified portfolios based on a few questions you answer.“Alternatively, first-timers could buy a cheaper tracker fund, which mimics the performance of a broad basket of shares or bonds, such as the MSCI World index. Fidelity Index World is one popular option, with a low annual cost of 0.12 per cent,” he added.What mistakes should first-timers avoid?Many experts say it’s also important for those starting out investing to do a bit of reading, and perhaps even experimenting with smaller amounts of money, so they can become comfortable with what happens in the stock market.(Getty Images)Coatsworth warns: “It’s common for people to make investments for the first time without proper research. They might choose a stock that sounds good but underestimate what could go wrong. It could be very easy to get swept up in the narrative of an exciting trend and pile in hoping for a short-term bump, but investing is always about the long term.“Just remember to think about any restrictions on accessing invested money such as penalty charges associated with Lifetime ISAs or understanding that pension money is locked away until you reach a certain age.”Ultimately for most people, the real question to consider is not whether they’ve reached £10,000 in savings.It’s whether some of their money has stopped having a job to do, and could work harder over the long term instead.When investing, your capital is at risk and you may get back less than invested. Past performance doesn’t guarantee future results.