A Stock Exchange announcement confirmed the deal, following legal approval for the merger last week, and will create one of the world's largest investment companies.
The company, which will trade as Standard Life Aberdeen, will hold £670bn under management.
Keith Skeoch, Chief Executive of Standard Life Aberdeen, commented:
“Today marks the culmination of many months of hard work and preparation by our business, and the beginning of a new chapter in our history as Standard Life Aberdeen plc. Our leadership team is in place and we have full business readiness from day one. Our people have worked exceptionally well together to complete the merger on schedule and we would like to thank them for this. The co-operation and collaboration we have witnessed bodes well for the on-going integration of the business, and in helping us create a world-class investment company for our clients, shareholders and our people.”
Martin Gilbert, Chief Executive of Standard Life Aberdeen, added:
“As ever our priority remains the delivery of strong investment performance and the highest level of client service. The merger deepens and broadens our investment capabilities, and gives us a stronger and more diverse range of investment management skills as well as significant scale across asset classes and geographies. We believe this will enable us to deliver an even better proposition and service to our enlarged client base.”
