Retail investors on interactive investor (ii) placed 22% fewer trades a day in the third quarter than in the second, owner Aberdeen Group said today (Wednesday). The platform averaged 28,100 daily retail trades, down from 36,100.Money kept coming in. Net inflows reached £2.5 billion (about $3.3 billion), up 32% from £1.9 billion a year earlier, and customer numbers rose 8% to 533,000.London's trading industry is coming home!According to BWC Benchmarking data cited by Aberdeen, ii handled 30% of UK cash-market retail trades and held 21% of all platform assets in the second quarter. Its numbers cover a large slice of UK share dealing.The pool is small by international standards: Britain has the lowest retail investment levels in the G7, with 23% of Britons invested in stocks.How ii Compares With AJ Bell and Other UK PlatformsAJ Bell, which is listed in London, has not yet reported July to September. In the April to June quarter it had 762,000 customers, 23% more than a year earlier, and took £3.0 billion in net inflows, according to its July trading update.Over the same three months, ii brought in £3.8 billion with 525,000 customers.The asset lines differ in scope: Aberdeen counts assets under management and administration, AJ Bell only those under administration.Hargreaves Lansdown is no longer listed after it agreed to a £5.44 billion buyout by a consortium led by CVC in 2024.At the end of June 2025, its last full year as a listed company, Hargreaves Lansdown had £172.7 billion in assets and more than 2 million active clients.App-based rivals report less often. Trading 212's UK revenue rose 72% to £277.6 million in 2025, according to its accounts.Trading Cools After a Record First HalfThe third-quarter figure is still 6% above the 26,600 trades a day recorded a year earlier. Activity climbed from late 2025 and peaked in the second quarter, the highest level in the seven quarters Aberdeen published today.Trading was "well above last year's average, albeit lower than the elevated levels earlier this year," said Jason Windsor, chief executive officer of Aberdeen.Net inflows followed the same path, falling from £3.8 billion in the second quarter in what Aberdeen called a seasonally quieter period. Year-to-date inflows of £9.3 billion are 58% higher than in the first nine months of 2025.Pension accounts grew faster than the customer base. Customers holding a self-invested personal pension (SIPP) rose 34% year-over-year to 131,000, a market that Trading 212 entered in March after a five-year wait.Customer cash fell to £8.3 billion from £8.6 billion at the end of June, though it is still £1 billion higher than a year ago.That pool faces a change from April 2027, when the cash ISA allowance for under-65s drops to £12,000 and a 22% charge applies to cash interest in stocks and shares ISAs.Assets at ii rose 19% since the end of 2025 to £111.8 billion, helped by market gains.Outflows Continue Elsewhere at AberdeenAcross the whole group, net outflows were £0.3 billion in the quarter. Aberdeen ended September with £578.9 billion in assets under management and administration, 4% more than at the end of 2025.Adviser, the platform for financial advisers, lost £0.7 billion for a second quarter in a row. The Investments arm lost £2.0 billion, as £2.5 billion left Insurance Partners, mostly from Standard Life's heritage book in run-off.Aberdeen kept its 2026 targets of at least £300 million in adjusted operating profit and about £300 million in net capital generation. In October it sold half of its Standard Life stake for about £430 million and said it will redeem £210 million of Additional Tier 1 debt in December.This article was written by Damian Chmiel at www.financemagnates.com.