Retail shops in Phoenix face a deadline this week to confirm efforts to keep shopping carts on site and avoid a $500 minimum fine.

Thursday’s deadline stems from a new Phoenix ordinance tied to the city’s shopping cart retrieval program that lets residents report abandoned carts.

The city already charges a per-cart fee for returns.

And now stores with carts have to share detailed information with city officials as part of a yearly certification.

Stores must either use locking wheel systems, or have launched a management plan to keep carts from leaving their property and ensure quick retrieval if they do.

Homeless people often use shopping carts to carry their possessions.