The equity buffer will rise from £150,000 to £250,000 with effect from Wednesday 24 February.
Santander offers interest-only mortgages, up to a maximum 50 per cent loan to value (LTV), and part interest-only, part capital and repayment mortgages, up to 85 per cent LTV.
For interest-only the £250,000 will be based on the deposit and equity at application. And for part and part, the £250,000 will be calculated on the equity at the end of the mortgage term.
Helen Harrison, head of intermediary distribution, Santander (pictured) said: “We last reviewed our interest-only buffer in 2016, when Office for National Statistics (ONS) data showed the average house price stood at around £205,000.
“At the end of 2020, the same data showed the average house price was nearer £250,000. By increasing our IO buffer we are ensuring customers have strengthened resources when they to need to sell-up and downsize to another property at the end of their IO term.”
