For some incomprehensible reason, one of my clients for whom I do payroll processing, has been getting a handful of basic rate tax code notifications even though that is the employees' only employment, and it has been incumbent on me to make long phone calls (90% waiting) to sort this out, and once the employee has authorised the conversation, HMRC have concurred to me that the persons should be on normal cumulative tax code.

Does anyone have any idea about what is going wrong with HMRC's internal machinations? - I am not happy as it makes more work for me, and the employees are not happy (until it is resolved, then they are delighted) that they are (temporarily) out of pocket.