One third of new lets are being agreed before the existing tenant moves out, says Countrywide.
The chain says that the average UK property is let within 32 days – the shortest time on record.
So far this year, it says, 33% of all new lets were agreed while the property is still occupied, up from 27% last year.
The average let agreed while tenants are in place is equal to 105% of the asking rent, equating to an average of £35 a month more than the asking rent.
In comparison, tenants moving into an empty property have more room to negotiate on the rent, knocking an average of £21 a month off what the landlord was looking for.
In London, 51% of new lets are agreed while there is still a sitting tenant in the property, up from 41% in 2014. At the other end of the scale, in the north-east a quarter of new lets are agreed before the existing tenant moves out.
Where a deal is agreed before the existing tenant leaves the property, there is an average of just six days between the existing tenant moving out and a new one moving in.
In one out of ten cases, a new tenant moves in on the same day that the existing tenant moves out.
Where a property hasn’t been let prior to a tenant leaving the property, the first week of marketing is when landlords are most likely to achieve the highest rent.
During the first seven days, the average let is agreed at full asking price, a figure which falls the longer a rental property is on the market.
The first weekend after coming on to the market is when most tenants view the property. In London’s fast-paced rental market, however, fewer landlords need to wait until the weekend to find a tenant. Twice as many lets are agreed on a weekday in London than in any other part of the country.
David Fell, research analyst, said: “In larger rental markets, more new lets are being agreed well in advance of the current tenant leaving.
“As a result we’ve seen void periods fall, with a growing number of landlords having a new tenant lined up over a month before their existing tenant leaves. While leaving some time for maintenance between tenancies is advisable, increasingly there’s just a matter of hours between a tenant moving out and one moving in.”
“In more competitive markets, the first tenant to view a home is often willing to pay a small premium to ensure the landlord takes the property off the market and that no further viewings take place.”