Face coverings are now compulsory for customers in shops in England but Police say they will only be enforcing the rules, including issuing the £100 fines, as a last resort – and officers will not be patrolling premises.
Coverings are mandatory in enclosed public spaces such as supermarkets, indoor shopping centres, transport hubs, banks and takeaways.
Police can hand out fines of up to £100 to those who do not comply.
But some retailers have insisted they will not enforce the rule.
Sainsbury’s and Costa Coffee said their staff will not challenge customers who enter their stores without masks, while Asda said enforcement was the “responsibility of the relevant authorities”.
But Waitrose will have staff at the entrance reminding customers of the rule, and Tesco will be selling face coverings at shop entrances.
Greggs and McDonalds said takeaway customers need to wear masks.