Larger homes appear to be going up for sale more frequently as a result of growing rumours about a capital gains tax (CGT) raid in October's budget, according to the largest property website in the UK.

According to Rightmove, there was "a flurry of activity at the top end" of the market in the week that ended on September 9. In comparison to the same period previous year, there were 15% more larger homes advertised for sale in Great Britain. These properties were classified as four-bedroom detached houses and all five-bedroom and larger properties. Furthermore, the number was higher than 20% in the east and south-west of England, which are home to some of the most well-liked rural and seaside areas in the country.

According to The Guardian, chancellor Rachel Reeves was reportedly thinking of including an increase in CGT revenue in the budget for October 30. The Resolution Foundation think tank pushed Reeves to reveal CGT and other details on Tuesday as speculation about tax changes to raise billions of pounds.

Rightmove said various factors could be causing the increase in owners of larger homes wanting to sell. One was falling mortgage rates following the Bank of England’s 1 August interest rate cut, and the expectation of more to come.

“Another factor is increasing speculation around a CGT rise,” the website said. “In addition to landlords, second homeowners of larger homes, in particular, could be hit by any increase to CGT, which may be leading some to cash out now.”

The report’s findings come a day after Rightmove rejected a £5.6bn offer from the Rupert Murdoch-owned property firm REA, saying it “fundamentally undervalued” the portal and its prospects.

In a separate release on Thursday, the Royal Institution of Chartered Surveyors (Rics) said there had been an increase, albeit a modest one, in the number of homes for sale, “with reports … suggesting this will continue”.

In its latest monthly survey, the surveyors’ trade body said the housing market was showing promise. “Buyer demand and sales activity are on the rise, with industry professionals anticipating further growth as we move into the final quarter,” it said.

Its data covering August showed more people were looking to buy a home, and that house prices were starting to increase “after almost two years of decline”.

However, Simon Rubinsohn, the Rics chief economist, said uncertainty surrounding further interest rate cuts and the forthcoming budget were “keeping the mood in check”.

The two most recent house prices surveys from Halifax and Nationwide have painted a picture of a reasonably robust property market.

Earlier this month Halifax named Manchester as the “first-time buyer capital of Britain”, because those taking their first step on the property ladder accounted for 75% of home purchases with a mortgage in the city last year.

Following an analysis, Santander, a major lender, identified the following areas as first-time buyer hotspots: the Surrey borough of Waverley, the London borough of Waltham Forest, which encompasses Walthamstow and Chingford, and the Nottinghamshire borough of Bassetlaw.

Santander examined which communities had experienced the largest rise in the number of first-time buyers using data spanning the years 2013 to 2023. Other "top rising neighbourhoods" were Merseyside's Knowsley and Essex's Harlow.