My solution to the Cleaner Code challenge (https://www.codeproject.com/articles/1083348/csharp-bad-practices-learn-how-to-make-a-good-code)

CleanerCode.fs

type AccountKind = Simple | Valuable | MostValuable

type CustomerStatus =
  | Unregistered
  | Registered of AccountKind * Years:int

let accountFactor kind =
  match kind with
  | Simple -> 0.9m
  | Valuable -> 0.7m
  | MostValuable -> 0.5m

let loyaltyFactor years =
  1m - decimal(min years 5) / 100m

let applyDiscount price status =
  match status with
  | Unregistered -> price
  | Registered(kind, years) ->
      price * accountFactor kind * loyaltyFactor years

Great job with the refactoring. Seeing examples like this make me want to look into F#... but then I see this and it drives me nuts:

Registered of AccountKind * Years:int

I am really curious about the thought process of whoever came up with that, instead of the much more obvious

Registered: AccountKind, Years: int

or

Registered of AccountKind, Years of int

I vote
Registered of (AccountKind, Years: int)
the same way its called later Registered(kind, years)

also make
price * accountFactor kind * loyaltyFactor years
into
price * accountFactor(kind) * loyaltyFactor(years)