There is a great incentive for families with this level of assets to reduce the size of their estate, according to Towry.
The company has stressed that retirees should enjoy their money, despite concerns such as care costs and protecting their finances.
It said one in ten UK households have assets totalling £1m or more.
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Someone who dies with total assets worth £1m could be hit by a £140,000 inheritance tax bill if married or £270,000 if they are single.
Ian Dyall, estate planning expert at Towry, said: "While people may have spent a lifetime building up their income for retirement, it may be that in retirement itself, many are reticent about using some of this money on what is important to them. "This could be providing for a disabled relative, helping their children or grandchildren financially, or passing money onto a favourite charity.
"Whatever your individual circumstances may be, your money is ultimately there to be enjoyed."
Towry used the example of a couple in their 70s who, through cashflow modelling, were found to have over £1m in surplus funds and used these to pay for private school fees for their six grandchildren via a mix of bare and discretionary trusts. This reduced inheritance tax liabilities.
Mr Dyall added: "It is important to remember that you must still be able to access some money for planned or unforeseen events, such as holidays or long-term health care.
"Cashflow forecasting allows you to see a clear path for your retirement, be that spending on yourself and your loved ones, while still keeping appropriate levels of money in reserve."