Computer technicans are threatening chaos at fast-food outlets, supermarkets, banks and airports unless they get a pay rise.

More than 100 staff from NCR - a company responsible for repairing computer breakdowns at KFC outlets, Aldi supermarkets and Sydney Airport's baggage handling systems - are planning to to walk off the job on Monday morning.

"In terms of industrial action in the IT industry this is easily the most significant one we've had in Australia," said Australian Services Union secretary Sally McManus. If the strike goes ahead, it might last up to a week, she said.