This figure is up from the 3.0% recorded in August and sits house prices during the month at a record high of £245,000.
According to the figures, average house prices rose over the year by 4.9% in England, 3.8% in Wales, 4.3% in Scotland, and 2.4% in Northern Ireland.
On a regional level, the South West saw the highest annual house price growth in England, up by 6.4% to £275,000 in the year to September - a rise of 3.2% against August. At the other end of the scale, the North East saw average prices increase by 3.3% over the year to September 2020.
In the capital, average house prices hit a record high of £496,000.
On a non-seasonally adjusted basis, average house prices in the UK increased by 1.7% between August and September 2020, compared with an increase of 0.1% in the same period a year ago. And seasonally adjusted, average prices were up by 1.8% over the month, following an increase of 1.1% in the previous month.
Anna Clare Harper, CEO of asset manager SPI Capital, comments: "For many, September feels like the distant past, but this index remains interesting and useful since it represents a more complete picture than comparable releases. A 4.7% increase in house prices, with mortgage approvals at their highest level since 2007, suggests a ‘mini-boom’. Many feel this will be short-lived, given economic circumstances and forecasts.
"However, the ‘fundamental’ drivers of housing demand are strong, and we are in an environment of low-interest rates, with reduced rates of new buildings coming onto the market and limited existing stock.
"Ultimately, increasing house prices are being driven by a combination of new priorities and new policy. Notably, many existing homeowners were spurred on to move by the combination of needing more space and the temporary Stamp Duty changes. As a result, and perhaps unsurprisingly, the increase in house prices was led by detached and semi-detached properties.
"It is interesting to note that new-build properties lagged behind existing properties, falling by 1.9%, despite the influence of the Help to Buy scheme.
"Returning to fundamentals - for investors and homebuyers alike, the important thing to remember is that capital growth is a great bonus, but shouldn’t be relied on just because lending is cheap."
Tomer Aboody, director of property lender MT Finance, adds: "With the mini-boom at full pelt over the past few months, buyers are desperately trying to get deals over the line in order to take advantage of the stamp duty holiday before the end of March. Unprecedented delays in mortgage offers due to staff working from home, coupled with the increase in demand, isn’t helping.
"While older housing stock has increased in value, new-build values have fallen over the past year. This may be because more space is at the top of buyers’ wish lists, both inside and out, which is something new builds aren’t known for. Developers may also have been too optimistic on pricing, and are now being forced to be more realistic, adapting to reflect demand and affordability. This could well force some change in the way new builds are designed in the future."
