Some stores send out “civil recovery notices” to shoplifters, saying they have to pay a flat fee within a set time – for example, a fee of $275 to be paid within 21 days. It’s doubtful whether these notices are legally enforceable in themselves, and you can refuse to pay them.
You don’t have any legal responsibility to pay the amount stated in the notice unless and until the store proves a civil claim against you for that amount in the Disputes Tribunal or the District Court. To do that, they need to show that you caused the specific loss they’re claiming, as opposed to simply claiming a “blanket” fee from all shoplifters.
If a store does prove their claim and obtain a decision in their favour from the Tribunal or the courts, they can use the available measures to enforce the decision – such as getting a warrant from the court for your property to be seized so they can recover the amount of their claim.