Results for the nine months ended 30 September revealed the milestone alongside other strong metrics.
The results showed the firm had increased inflow of funds from £10.46bn in 2017 to £11.75bn, an increase of 12%.
The company also retained 96% of clients and increased its net inflow of funds by 15%, from £6.66bn in 2017 to £7.68bn.
Group funds under management rose from £85.7bn in 2017 to £100.6bn this year, an 11% increase.
Andrew Croft, chief executive, said: “Building on the exceptional growth we achieved over the last two years, I am pleased to report continued growth in the third quarter. Gross flows, at £3.83 billion, were 7% higher than the prior year comparator, which itself was up 28%.
“This takes the year to date gross flows to £11.75 billion, growth of 12%.
“With continued strong retention, net flows for the nine months were up 15% to £7.68 billion, taking funds under management to a record £100.6 billion, up 11% since the start of the year and 17% over the 12 months.
“We have delivered this continued growth despite both tough comparatives and a more challenging environment for the industry, once again demonstrating our resilience in these market conditions.”
He added: “There remains growing demand for high-quality financial advice, notwithstanding the current macro and geo-political uncertainty.
“With the strength and professionalism of the Partnership, together with the breadth of our client proposition, we have a major and sustainable competitive advantage.
“Consequently, we remain confident in our ability to grow our business in line with our stated objectives over the medium-term.”