The case against Daventry-based company Extreme GB LTD was the 17th and final in a three-year Croydon-led nationwide clampdown on knife sales to children which was backed by the Home Office and National Trading Standards.
During a pilot test purchase programme a 13-year-old volunteer, working under the guidance of Croydon Trading Standards, made 100 attempted test purchases online, of which there were 41 sales.
It is illegal to sell an axe, knife, knife blade or razor blade to anyone under 18.
In one case Topline Wholesale Ltd, based in Derby Street, Manchester, sold a hand axe to the teenager via eBay.
The company was fined £8,500 and ordered to pay £10,500 in costs.
Another company, Bright Associates Limited of Wickham Road, Croydon, sold a six-piece knife set to the 13-year-old leading to a fine of £11,725.
During the purchase the volunteer was asked to enter a date of birth and entered his true date of birth, showing he was 13-years-old.
Councillor Manju Shahul-Hameed, cabinet member for communities, safety and business recovery said: “Selling knives to children is incredibly dangerous and too many lives have been lost by the reckless actions of retailers.
“I hope this series of prosecutions sends out the clearest possible message that they must put tough measures in place to stop underage sales or risk going to court.”
And Lord Toby Harris, chair of National Trading Standards thanked all teams involved particularly Croydon Council’s team which led the cases.
He said: “All 17 prosecutions resulted in guilty outcomes which demonstrates what we’ve been saying all along: the law is clear and if a retailer has adopted the correct procedures and ensured they are implemented there is no offence.”