From July 1, people looking to sell or give away kittens, cats, puppies or dogs in New South Wales will need to include an identification number in advertisements.

The laws will be put in place to promote responsible cat and dog breeding and to help identify problematic breeders and enforce animal welfare laws.

The identification number can be either:

The rules will apply to all advertisements.

The law will apply to those in newspapers, local posters, community notice boards as well as all forms of online advertising, such as the Trading Post, Gumtree and social media sites.

The changes have been implemented in response to the Parliamentary Inquiry into Companion Animal Breeding Practices.

The changes will help people who want to buy a cat or dog search the New South Wales Pet Registry to see the animal's:

A breeder identification number search will also display any business name listed in the registry.

Sellers can be issued an on-the-spot fine by an enforcement officer of $330 if they do not include an identification number in an advertisement.

Failure to display an identification number, or falsification of a number can also carry a maximum penalty of $5500 in court.

Welfare officer with the Far South Coast branch of Animal Welfare League NSW Wendy Cook said the stronger regulations about breeder identification was a step in the right direction, provided it gets enforced.

"It they're going to police it, it will be great," Ms Cook said when learning of the move.

"And it it starts to affect numbers it will be good news for us as well.

"I think people will need to be hit in the hip pocket before they take notice though."

Of particular note, Ms Cook said administrators of Facebook trading pages, popular with animal sellers, will need to pay close attention to ads they host to ensure they aren't facilitating people breaking the law.

Ms Cook said desexing and microchipping companion animals taken into their care, or ensuring they already were, prior to re-homing was "just part of what we do" at AWLFSC.

She encouraged people wishing to avoid getting into strife because they aren't a licensed breeder to contact AWL to take advantage of its desexing program. Subsidised vouchers are available to those on certain government welfare payments.

Call AWLFSC on for details on 0400 372 609.

The New South Wales Pet Registry can be found at www.dpi.nsw.gov.au

If you suspect that an advertisement does not include a valid identification number you should contact RSPCA, Animal Welfare League, or the police.