Its full year results show that the Society's mortgage assets increased by £2.5 billion (9%) to £29.4 billion, five times the rate of market growth.
At 31 December 2015, only 0.24% of mortgage balances were 2.5% or more in arrears.
Net interest income stood at £363.9m - £22.6m higher than the previous year, primarily as a result of growth in mortgage assets, according to Coventry.
Savings balances grew by £2.0bn (8%) to £25.4bn.
Mark Parsons, Coventry Building Society Chief Executive, said: “It continues to be a tough time for savers and in a low interest rate environment it is important that we provide competitive savings products not just today, but reliably and sustainably into the future.
We are achieving this. At the end of 2015 our average savings rate was 1.97% compared to a market average of 1.11%. Furthermore, at the end of 2015 our average variable rate on cash ISAs was nearly two and a half times the market average.
Our ability to do this, whilst maintaining a very competitive mortgage portfolio, is underpinned by the high quality of our mortgage lending, which results in extremely low impairment charges, as well as low cost operations. We continue to lead the sector in cost-efficiency, with our management expense ratio of 0.42% remaining significantly lower than that of our peers.
We also strive to keep things simple, transparent and easy to use. To help achieve this we have commenced a four year technology programme that will deliver improved processes and systems, and provide our members with enhanced service options."
