Why holiday work is the hardest to verify
During term, a school can see the service happening. Staff notice whether bins were emptied and whether the front office was serviced, and problems surface within a day. Over a holiday period nobody is present, the work happens across several weeks, and by the time anyone returns the evidence is a general impression of a building that has been cleaned.
That is exactly the situation where a specific record matters. A carpet in a meeting room that was not treated will not be obvious in February, particularly against the general improvement from everything else that was done. Without a completion record, the only way to check is to ask, and the answer will be based on memory several weeks after the fact.
