Animal Welfare Act 2006 (England
and Wales) - Docking
As from April 2007 it will be illegal to dock
puppies' tails (other than for therapeutic
reasons or if a breeder can submit evidence
to a Veterinary Surgeon that the dog is of a
specified type to be used for work, rescue,
armed forces, police, pest control).

Regulations pertaining to this law
approved April 2007 by England
and Wales separately.  It will not be
permissible for docked dogs to be exhibited
at shows where the public pay an entrance
fee.

After the dates on which the regulations on
exemptions came into force, members of
the public should report any breeders to
their Local Authority/RSPCA whose litters'
tails are known to have been removed
without the required certification.
Anyone flouting the law can be prosecuted
and fined £20,000, possible imprisonment
and be banned from keeping animals (which
could mean that other animals in their care
could also be confiscated.
No-one should buy a docked puppy without
accompanying certification to prove that the
dog has had its tail removed legally and it is
intended as a working dog under the
categories listed in each region's regulations.
This Veterinary certificate will be proof that
the dog has been docked legally and will be
important in prosecution cases. The dog also
has to be microchipped with associated
certification.
N. IRELAND – As from 29 March 2011 the
N Ireland Welfare of Animals' Act came into force . 
In Section  6 of the Act – Docking of dogs' tails wef 1/1/13 -
3a This clause prohibits the docking of a dog's tail, otherwise than for the purposes of its medical treatment by a veterinary surgeon or to safeguard its life or where dogs are working dogs and could benefit from prophylactic docking by reducing the risk of future injury while working "certified working dogs". These dogs are subject to certification and identification regulations and are the following: Spaniels and combination of breeds, Terriers and combination of breeds, any breed commonly for hunting and combination of breeds, any breed commonly used for pointing and combination of such breeds, any breed used for retrieving or any combination of such breeds.
  It will be an offence to take (or cause another
person to take) a dog from Northern Ireland for
the purpose of having its tail docked. The clause also introduces a ban on the showing of dogs when the xhibitor pays a fee or there is a public admission fee
and where the tail was docked after introduction of
the new Welfare of Animals' Act.