Belfast shops were permitted to open three hours earlier than usual on Sunday so healthcare workers and the vulnerable could buy essentials.
Belfast City Council relaxed its Sunday trading restrictions last week in order to give these groups extra time to shop during the coronavirus pandemic.
It is not known how many shops and supermarkets took up the offer and opened their doors from 10:00 BST.
The temporary arrangement will be in place until further notice.
However, a spokesperson for Belfast City Council said it would not apply on Easter Sunday.
Under normal circumstances, larger shops with a floor space of more than 280 sq m (334 sq yd) are only permitted to sell goods from 13:00 to 18:00 Sundays.
Sunday trading has been a controversial issue over the years in the city.
In 2017, a plan to extend trading hours on 18 Sundays was heavily defeated in a council vote.
Retail groups were split on the idea and the shop workers' union, Usdaw, opposed it.
However, during the coronavirus pandemic, some elderly customers and NHS workers were unable to purchase some essential supplies due to panic buying.
Many supermarkets and retail chains have since introduced limits on buying certain products to ensure more people can access the goods they need.
Social distancing rules have also led to the formation of queues outside many supermarkets, as shopkeepers limit the number of customers who are allowed to enter their premises at any one time.