This year's campaign is the best supported to date, with thousands of retailers having applied for special promotional materials to adorn their stores.
"The basic concept of National Independents' Week is to send a signal to locals that their store is a focal point in the community and the people who own it are fellow members of the community and not managers appointed by a distant corporation," said Alan Toft, chair of My Shop is Your Shop campaign, which organises the event.
Seven million money-off coupons will be printed in The Sun, The Scottish Sun and Liverpool Echo on 29 May . The coupons, which offer a total saving of £2.60, include promotions on Monster Munch, Carling, Booker's Euroshopper Energy Drink and Landmark's Eridge Vale cider. They can be redeemed at any local store.
Retailers that took part in last year's scheme reported that sales of promoted products grew 15.7%.
Wednesday is also National Cuppa Day, in which shoppers will be offered a free cup of tea and biscuits. Tea bags will be donated by Tetley, sugar by Tate & Lyle and biscuits by McVitie's.
Wholesalers such as Sugro and Bestway are also supporting National Cuppa Day by sending out promotional materials and foam cups to their members.
Wholesalers and suppliers will also support the event by encouraging retailers to take part and senior members of staff to participate.