While this £7.1bn figure was largely consistent with the first half of the year, the bank saw its share of the market dip slightly from 12%.
However, it noted that its mortgage approval share was around 14% in the quarter, up from 12% in the previous three months.
The bank also revealed that more than 60% of existing customers transferring to a new fixed rate mortgage deal switched digitally.
This was part of its focus on customers using digital services, and as a result RBS reported 5.2 million customers regularly using its mobile app (14% up on December 2016) with digital service transactions 7% higher compared to Q3 in 2016.
RBS said its overall mortgage portfolio loan-to-value (LTV) was 56%, in line with FY 2016, and LTV on new mortgage lending was 70% for the year to date.
The bank reported a £392m for Q3 2017, the third successive quarter of profit, and an overall profit of £1.33bn for the year to date.
RBS added that it remains on track to achieve all of its 2017 financial targets.
However, the is still being dogged by the scandal relating to its Global Restructuring Group in the UK.