Badrul Alom, who owns Rivaj of India in Wrightington, was charged following an investigation by West Lancashire environmental health officers and Lancashire trading standards.
The Chorley Guardian reports that officers found traces of peanut protein in three chicken curries ordered from the restaurant via the Just Eat website in November 2016, despite specifying they were for a diner with a nut allergy.
Preston magistrates heard Alom was informed of the results and a follow-up visit was arranged for February 2017, when officers found traces of peanut protein in samples of a chicken korma dish and several dry ingredients which had been decanted in to storage tins.
The chairman of the bench said they considered it a “very serious matter with the potential harm that could have been caused”.
Alom was fined £3,000, and must pay a £100 surcharge and £1,625.62 costs after pleading guilty to three food safety offences and three of supplying dishes not being of the nature demanded by the purchaser.
He confirmed he now speaks to customers before processing orders received through Just Eat to check if they have allergies, and has changed the way dry ingredients are decanted.
Since the EU Food Information for Consumers Regulation came in to force in 2014 all foodservice businesses have been required to list 14 allergens including nuts, gluten and mustard on menus, or have their presence communicated by staff.
In 2016 restaurant owner Mohammed Zaman was jailed for six years for manslaughter after the death of a customer with a peanut allergy in what was thought to be the first case of its kind.
According to the Food Standards Agency an average of ten people die and around 5,000 are hospitalised each year after suffering allergic reactions.