Owners of XL bully dogs must have their pets registered or put down within the next week or face a criminal record or fine, the government has warned.
The American XL bully is set to be banned in England and Wales from 1 February following a spate of recent attacks - some fatal - involving the breed.
Scotland has also introduced its own legislation which will essentially mirror the ban in England and Wales, though it is set to come in at a later date.
Owners must either have their dogs euthanised or apply for an exemption certificate, which involves registering their pets with authorities.
Those whose dogs are registered will also have to comply with restrictions to ensure their pets do not pose a danger, including having them microchipped, neutered, and kept on a lead and muzzled when in public.
The registration system for the breed will close at noon on 31 January, and owners have until then to obtain their certificate.
The UK's chief veterinary officer, Christine Middlemiss, urged people not to leave registration to the last minute.
"If you want to keep your dog, you should register it now," she said.
"If you are unsure if your dog is an XL bully or whether any puppies may grow up to be of this dog type, you should comply with the relevant requirements and restrictions."
What does the ban mean?
From 1 February, anyone found in possession of an unregistered XL bully, or who does not adhere to the strict conditions, will face a criminal record and an unlimited fine.
Owners wishing to keep their XL bully will have to pay a fee - £92.40 in England and Wales - to register the pet.
According to the government, over 30,000 XL bully dogs have been registered since the law was announced.
The government says it has also received more than 100 claims via its compensation scheme - for costs such as reimbursement for euthanasia - from owners who have had their exemption request rejected or chosen not to keep their dogs.
The ban involves two stages, the second and final stage of which will come into force on 1 February.
The first stage came into force on 31 December, when it became illegal to have an XL bully in public unless muzzled and placed on a lead.
Breeding, selling, advertising, rehoming, abandoning and allowing one of the dogs to stray was also made illegal in England and Wales from that date.