Hargreaves Lansdown reported net inflows of £2.9bn in the four months to the end of April 2019, £400m lower than the same period in 2018.
Net inflows since July 2018, when the company’s current financial year started, were £5.4bn, £1.2bn lower than for the same period last year.
But the FTSE 100 company's trading statement revealed positive market movements of £9bn helped its assets under management reach £97.8bn at the end of April 2019, the highest it has ever been.
The inflows include £267m of assets Hargreaves Lansdown took on from the Witan Savings Plan and £399m of inflows into its Active Savings Plan, a cash management service launched in September 2018.
Chris Hill, Hargreaves Lansdown's chief executive, said: "We are pleased with the strong tax year end, delivering net new business of £2.9bn and welcoming another 53,000 net new clients despite the market backdrop.
"It is also pleasing to see the benefit of our investment coming through with Active Savings continuing to gather momentum and the announced transfers of clients and assets from Witan Investment Services, JP Morgan and Baillie Gifford.
"Whilst political and macro-economic uncertainty remains, we are confident that our continued focus on the needs of UK investors and savers means that we are well positioned to deliver attractive growth."
The 53,000 new clients Hargreaves Lansdown took on over the four month period took its total number of clients to 1.18m.
Despite the slower pace of inflows, the company's revenues rose to £159m, up from £150m in the same four month period of 2018, as a result of improved margins.
The company’s share price has largely been unaffected by the update, and is down less than 1 per cent in early trading this morning.