The platform and investment business said it was against a "challenging market backdrop".
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Gross inflows for the year were £9.3bn compared to 2022's £10.1bn.
However, it said it now had record assets under management of £70.9bn, up 11% for the year, driven by the net inflows across the platform and favourable market movements of 4%.
It added customer numbers increased by 50,880 to close at 476,532, up 12% for the year, as AJ Bell's dual-channel platform continued to deliver "strong organic growth in both advised and D2C customers".
Total advised customers increased by 13,885 to 159,256, up 10%, while total D2C customers increased by 36,995 to 317,276,, a 13% increase.
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CEO Michael Summersgill said: "I am pleased to report another year of continued organic growth for AJ Bell, with the number of customers using our platform increasing by over 50,000 thanks to our quality of service, exceptional value and easy-to-use products.
"Our dual-channel model, which serves the needs of both advised and DIY investors, once again demonstrated its strength as we delivered over £4bn of net inflows onto our investment platform. This contributed to an 11% increase in platform assets under administration which ended the year at a record £70.9bn."
He added: "Our investments business enjoyed another year of significant growth, fuelled by strong demand from advisers and customers for our straightforward and low-cost investment range. This drove net inflows of £1.65bn, up 57% compared to the prior year. Combined with strong five-year investment performance, this has resulted in assets under management increasing by 68% in the year to close at £4.7bn.
"At an industry level, we continue to engage with government on potential ISA reforms, with our focus being on simplifying the existing ISA landscape to make it easier for retail investors to navigate. We believe this will encourage a greater number of people to invest via ISAs which would benefit UK-listed firms given the natural home bias exhibited by retail investors.
"The long-term growth drivers of the investment platform market remain strong, and we look forward to announcing the annual results for what has been another successful year for AJ Bell in December."