Assets on the Transact platform increased by 18.6 per cent to £33bn in the year to the end of September.
The platform's parent company, Integrafin, posted net inflows of £979m for the three months to the end of September and £4bn for the financial year.
While markets were hit by recent volatility, outflows from Transact were at their highest level in more than a year at £537m.
But these were outdone by inflows, which at £1.5bn were also near their highest level over that period.
Ian Taylor, Integrafin's chief executive, said: "We report another positive [funds under direction] update in what is becoming an increasingly challenging market environment.
"Net inflows for the financial year were 11.7 per cent higher than last year and outflows have decreased as a proportion of opening [funds under direction]."
Integrafin listed on the London Stock Exchange earlier this year and after completion of the lock-up period for the non-management principal selling shareholders in August 2018, "significant transactions" in the company's shares took place on the Transact platform.
This resulted in a £58m increase in net inflows. After removing these transactions inflows were 10.2 per cent higher than last year.
Since listing Integrafin's market cap has increased from £649m to £1.03bn.