A night-time surcharge is the supplement some tradespeople add to the normal price when the work is done at night, outside usual working hours. It is common in emergency services such as locksmiths, plumbers or electricians.
What matters is not so much that it exists as that you are told about it beforehand. If you are given a daytime price and then a supplement for the time of day turns up on the invoice, it is an unpleasant surprise.
With us, day or night, you get a fixed quote before we start, stating everything you will pay. If you accept it, that is what you pay; if anything changes once we see the job, we tell you before carrying on. More under emergencies.