Mortgage Advice Bureau research claims this is the first time this has happened since the Bank of England base rate was lowered to 0.5% in March 2009.
The data suggests borrowers are increasingly motivated to lock into fixed rates while mortgage pricing remains low. In comparison, just 91% of homebuyers fixed between February and April this year, and April 2014 remains the only other time where 96% of homebuyers have done so.
Some 92% of remortgage customers also fixed their rates in both August and September.
This is the highest proportion recorded since June 2014 when 93% of remortgaging homeowners opted to fix. The intervening period saw fixed rate popularity for remortgages fall as low as 85% in December 2014.
The average 2-year fixed rate rose from 2.68% in August to 2.72% in September, marking the first rise after 12 months of consecutive record lows. Meanwhile 5-year fixed rates also rose for the first time since August 2014, while 2-year trackers rose for the second successive month.
In contrast, the average 3-year fixed rate reached a new low of 3.10% in September, down from 3.11% in August and 3.71% a year ago.
Brian Murphy, head of lending at Mortgage Advice Bureau, said: “Sooner or later, the predictions of an interest rate rise are going to become a reality and some lenders have started to act ahead of this to ensure they are not short-changed.
“Borrowers should not be too alarmed by September’s jump in pricing, as there was only a slight increase and 3-year fixed rates continued to fall. All the same, it is a timely wake-up call that these rates are not here to stay forever.”
