The London Stock Exchange has started transferring its share trading operations to the MillenniumIT platform and is gearing up to go live on 13 September.
The project's phase one is underway. The LSE has sent technical specifications to companies that link into the exchange and set up a website to keep clients up to date with the project and any changes.
In March, the LSE will give partners access to the non-live test environment.
"Access to development resource will give them the chance to see if their systems work on Millennium when it is not live," said a spokesman.
During March, the LSE will put the first software code into the non-live test environment. The second and third releases will follow in April and May.
The company will give full access to development services in mid-June, with a dress rehearsal planned for early July.
The LSE plans to complete phase one of the project on 13 September, when Millennium IT goes live.
Yann L'Hullier, CTO at trading venue Turquoise, said that the LSE's plans to launch in September are "very ambitious".
"When we set up Turquoise we had no customers to worry about so it was easier. But the London Stock Exchange is a primary market with a massive number of customers."
If there is doubt among customers about meeting the deadline there could be problems, he said. "It is important that customers support the plan. If they do not believe the feasibility, they will not be focused."
L'Hullier said an October or November deadline might have been better.