Costs go to whatever code is nearest
It looks like admin until a claim needs the cost record behind it and there isn't one.
What's happening?
Under deadline, invoices get coded to whatever is open and plausible: the concrete goes to groundworks because that code has budget left, the extra labour to prelims because nobody set up a code for the disruption it actually served. Each shortcut is invisible - the total is right, only the story is wrong.
The story is what gets bought later. A disruption claim needs the cost of the disruption, not a smear across six codes; a variation needs its own cost record; a final account negotiation needs cost that reconciles to something. Coding discipline is dull exactly until it is load-bearing: codes that mirror how the money will need to be argued, set up when the job starts, policed monthly in the CVR - so when the claim comes, the record already exists.
The solution
Costs filed the way they'll need to be argued.