The lender has received 3,274 applications with a combined value of £2.4bn during that time, and issued agreements in principle worth £8.8bn.
The firm has completed 1,375 loans in total since launch.
Last week, it completed its largest and most complex loan to date, a £17.4m, five-year buy-to-let facility for a London-based landlord.
The facility refinanced 40 properties in London, comprising 160 units, at a rate of 4.99 per cent with one per cent interest deferred.
The broker was Liubov Vaskevych at Your Mortgage Advisor, whose role in the deal included securing reassurances to help overcome planning irregularities which existed on some of the properties.
Jonathan Samuels, chief executive at Octane Capital (pictured), said: “Completions of £1bn is a significant milestone and reflects the exceptional efforts of our team over the past four years. We’ve evolved into a hybrid platform since launching, offering product-less solutions and buy-to-let products.”
Mark Posniak, managing director at Octane Capital, added: “We’re only as good as the people we work with, and I’d like to thank all our broker, legal and surveying partners. We’re looking forward to hitting £2bn.”