AN entrepreneur who dropped out of medical school at 19 to become a pub doorman has sold the till software business he runs to a Swedish payments giant in what looks likely to have been a seven figure deal.

The takeover of intelligentpos by iZettle provides a lucrative vote of confidence in a business that has achieved dramatic growth in the three years since Robin Knox started the business on his kitchen table.

Mr Knox, 29, had the idea for developing an iPad-based app after he was quoted a £9,000 set-up fee for two tills he wanted to use for an indoor paintballing venture he established.

He built the app and the intelligentpos business with Paul Walton a technology manager with whom he worked during a spell in the night club trade. The retail app developed by intelligentpos runs on an iPad linked to a barcode scanner.

intelligentpos reckons the point of sale apps it supplies for £39 a month provide all the functionality of systems used by big businesses at a fraction of the cost of other till systems.

They can be used for tasks such as stock control and financial reporting.

The business has signed up more than 1,000 customers for its apps, which are targeted at firms in the retail and hospitality sectors and mobile businesses.

Its client list includes Underbelly, the UK's biggest festival operator. The company’s systems were used on more than 80 terminals at this year’s Fringe festival in Edinburgh

Sales increased by 300 per cent last year, to more than £1m.

The cash and shares acquisition will allow iZettle to offer a wider range of services to the small and medium sized enterprises its targets. It has focused on card payment processing.

Mr Knox noted the deal provided the opportunity for intelligentpos to join forces with a business that has been achieving rapid growth in that market.

It was concluded around 12 months after the company received a takeover approach from iZettle, and three years after the two firms started working together.

“It just created a real opportunity for us to create a one-stop shop for payments and point of sale, we thought this is fantastic,” said Mr Knox.

He believes the enlarged business can expand quickly by winning business in what is a consolidating market from the providers of traditional cash registers.

The two founders will stay with the business and have shares in the enlarged firm.

Mr Knox declined to disclose the price of the deal but said he was pleased with the valuation attached to the firm, adding: “It’s a significant endorsement of all the efforts of the team.”

Asked what the secret of the firm’s success was, he said: “Thinking we could do it and having the blind determination, the can do attitude. It was just a couple of guys sitting in a kitchen who believed in the impossible.”

Jacob de Geer, chief executive and co-founder at iZettle, said: “Via the acquisition of the talented team and great product at intelligentpos, iZettle takes yet another step towards its mission of providing small businesses with a wide range of services and features that are critical to helping them grow and build.”

iZettle is expected to make a significant investment in intelligentpos, which will remain based in Edinburgh.

Staff numbers are set to nearly double from 45 to 80 over the next year.

intelligentpos raised £500,000 growth funding last year from the 24Haymarket group of investors.

It also won £50,000 government funding through the Scottish Edge awards.

Mr Knox moved into business after helping to run the Cavendish nightclub in Edinburgh for Luminar. His first business was a paintball operation opened in vacant warehouses that offered relatively easy access for city dwellers.

He dropped out of Edinburgh medical school in 2006 in spite of enjoying the practical side of his training. “Studying felt so unnatural, I just loved working,” recalled Mr Knox.