Michael Briggs, 24, of Thicket Drive, was fishing at Harthill Reservoir last August when he was approached by a warden and asked to produced his licence.
Worksop Magistrates’ Court heard that Briggs thought he had purchased a day permit online the day before.
But when that was shown to be not the case, he put it down to a banking or technical error that had prevented the purchase from going through.
He then immediately called his mother, who bought a licence for him.
Briggs, who was not in court, was fined £60 and ordered to pay £127 costs and a £20 victim surcharge.