Interactive Investor have a stated policy of acknowledging all complaints within 3 working days if they can't be resolved before then, however, I've had cause to complain twice recently about the management of my SIPP and have found them to be woefully inadequate in meeting this target - it's taking weeks, not days, to elicit any form of response from them whether the complaint is made via their website or by letter. This is not a company that takes good customer service seriously.