Not sure if this is relevant or not https://www.google.com/url?sa=t&sou...FjABegQIHhAB&usg=AOvVaw1ii4Wdeh5XOuyhFX6xWvR8 the 424 code could relate to a tax adjustment?
If he earned £116k p.a. then his code would not be "L" as he would no longer be entitled to the standard tax free personal allowance.Maybe the OP would like us to know he earns £116.5k p.a.
sometimes takes a bit of a wait but i've phoned up HMRC a few times and they are super helpful.