Police have not fined anyone in Northern Ireland for failing to wear a face covering.
It became compulsory to wear a face covering in enclosed public spaces on Monday 10 August.
The Department of Health said breaches could lead to a fixed penalty notice of £60, reduced to £30 if paid within 14 days.
Responsibility for enforcement has caused confusion, with police saying it would only be used as a last resort.
The Police Service of Northern Ireland (PSNI) previously said the primary responsibility for enforcing the wearing of face coverings would lie with shop owners.
Emma McMahon, who co-owns a shop in Belfast, said it was not reasonable to expect business owners to bear the brunt of the work enforcing the legislation.
"I do think it is unfair that the responsibility is put on to the shop owners," she said.
"I would have to employ another person at the front door to police this on a very local basis and I simply can't afford to do that.
"We're finding that the vast majority of customers are following the rules and wearing masks and there's only maybe one or two people a day that aren't wearing masks.
"Whenever a customer has come in without a face covering, I haven't confronted them because I don't feel comfortable enough to do so, in case there's a medical reason behind that.
"We are really dependent on the goodwill and trust that people will wear their masks and certainly customers have as much responsibility as owners to help us all get through this."
Ahead of the rules coming into effect, the PSNI said: "Where necessary, officers will continue to engage, explain and encourage people to make the right choices and this includes the mandatory wearing of face coverings on public transport, in shops and other public enclosed spaces.
"The primary responsibility for ensuring compliance lies with transport operators and businesses but where police become involved, we will do so on the basis of the four 'Es' and only use enforcement as a last resort, when all other approaches have been unsuccessful."
Glyn Roberts, chief executive of Retail NI, said the scope of the legislation meant it would be difficult to enforce.
"It's not surprising there haven't been any fines in the first week," he said.
"I think it's going to be a very difficult situation to police and first and foremost, it is up to the individual shopper to obey the law.
"The police can't be everywhere and indeed it's very clear retailers and their staff are not required to enforce this, so it is very much up to the individual shopper to play their part in this.
"I think the big challenge is complacency and everyone has to do their bit to ensure that we avoid a second wave or any further significant increases in transmissions."
Does everyone have to wear a face covering?
The NI Direct webpage carries advice for people who are indoors in circumstances where it is not possible to wear a face covering, for example, where they are eating or drinking in a restaurant, pub or café, or are exercising in a gym.
In these circumstances, it said it was acceptable not to use a face covering, but you should replace it as soon as practicable afterwards and maintain social distancing of at least 2m if you are in an enclosed space undertaking physical exercise.
Other circumstances where it may be difficult for some people to wear face coverings, include:
- Physical illness;
- Where it is distressing for someone to cover their face;
- Where someone is accompanying a person who relies on lip reading to communicate;
- The reasons for not wearing a face covering may not always be visible.
There is no need to get a letter from a doctor or government to show that you do not need to wear a face covering. If you have a condition which means you cannot wear a face covering you only need to say, if asked, that you cannot wear a face covering because you are exempt.