Platforms must transfer up to £25bn of assets into unbundled charging structures ahead of the sunset clause in March.
Cofunds, Old Mutual Wealth and FundsNetwork still have billions of pounds-worth of assets to move.
Cofunds says 30 per cent of its assets under administration are yet to be moved to clean share classes. The latest accounts of its parent company, Legal & General, show Cofunds held £37.9bn in retail assets and £36.7bn in institutional assets at the end of June.
Old Mutual Wealth says 12 per cent of its Isa and collective investment assets are in a bundled adviser fee structure. A further 6 per cent have an unbundled adviser fee but a bundled platform charge and will also need to move to clean pricing.
The provider has £32.9bn in assets under administration but this includes pension assets, which are unaffected by the sunset clause. Old Mutual Wealth declined to give a figure for Isa and collective investment assets only.
Old Mutual Wealth and Cofunds say they will move their remaining customers to clean share classes by early 2016.
FundsNetwork declined to give details on the level of assets still in bundled charging structures. Its total AUA is £60.2bn.
The Lang Cat consulting director Mike Barrett says: “We estimate there could be £25bn AUA, which needs to move to unbundled charging. This could impact up to half a million investors, so the scale of the communication challenge is huge. If platforms bulk transfer their remaining assets, they will suddenly have a large non-advised book of low case-size investors, which could pose another challenge.”