Quilter expects the initial migration to its new platform to begin in early autumn, when the assets of about 100 adviser companies will be transferred from its existing system.
If the migration is successfully completed by the end of 2019, the wealth manager expects the total cost of the programme to be at the upper end of its current £120-£160m guidance range.
In its annual financial results for the year ended December 31, 2018, published today (March 12), Quilter reported it had incurred costs of £79m since the project had commenced in May 2017.
Quilter soft launched its new system last month and the wealth manager reported the system, processes and controls were "progressing well" in a live environment.
The next phase of the replatforming programme will incorporate full adviser functionality and is currently undergoing testing expected to be completed by early summer.
Quilter stated its migration planning was at an "advanced" stage with the company aiming to migrate an initial 10 per cent of assets under administration from its existing platform, equivalent to assets from about 100 adviser firms.
The wealth manager stated: "Once we have incorporated feedback from this into our processes, we will continue migration of the remainder of the book in appropriate phases considering, amongst other things, the time of year and market conditions."
But Quilter said the timeframe for completion could be extended slightly as the firm was keen to avoid the chaos seen at other platforms last year.
Paul Feeney, chief executive of Quilter, said: "Our overriding principle is that high quality delivery is of the utmost importance and we are enhancing our detailed plans to ensure customers and advisers are well supported throughout the transition period.
"This, together with the challenges imposed by the need to train a large number of advisers on a new system, are key issues which have been highlighted in our reviews of a number of problematic high profile platform transitions across the UK financial services industry in recent years.
"As a result, we are considering adding additional adviser/customer call centre capacity and/or taking a more gradual approach to migration, which could extend the project timeframe slightly."
Mr Feeney said if Quilter decided it was in the best interests of both customers and advisers that programme completion was extended into the first half of 2020, he expects "modest additional programme costs".
Quilter reported an adjusted pre-tax profit of £233m for last year, up 11 per cent from £209m in 2017, and an increase in total fee revenue of 8 per cent to £788m.
The wealth manager saw a drop in assets under management at £109bn - down 4 per cent year-on-year from £114bn in 2017.
Quilter reported this was as a result of its £2.7bn net flows being more than offset by negative market performance of £7.8bn.
Mr Feeney said: "Quilter performed well in 2018 despite increasingly challenging market conditions as the year progressed.
"We are delighted to report record profit with adjusted profit up 11 per cent and adjusted diluted earnings per share up 15 per cent.