Transactions fell by 11.8% last month, compared to the same period in 2017, according to HMRC.
Between February and March this year sales fell by 7.2% alone.
Kevin Roberts, director, Legal & General Mortgage Club, said: “Transactions have remained broadly flat for some time now, as the lack of housing supply and rising demand continues to take its toll.
“Not only is this limiting the options available to potential borrowers looking to buy their first property, but it’s having an impact higher up the ladder too, with many homeowners opting to improve rather than move.
“However, there are still plenty of reasons to be cheerful and it remains a good time to get a mortgage.
“Interest rates and mortgage rates are still close to their historic lows, and now is still an opportune time to speak with a mortgage broker and explore your options. Those who wait may find rates are not so favourable in six to twelve months’ time.”
Jeremy Leaf, north London estate agent added: “Transactions are a much better indicator of market health than the ups and downs of house prices for those of us at the coalface.
“And these figures, which of course reflect activity over the past few months, show the market to be softening but not collapsing as buyers and sellers seek to establish fair price levels.
“Those that do are clearly getting on with moving, whereas those that don’t are just getting left behind.”