Complaints made to local councils about barking dogs are common. Your council will have an established procedure for investigating, and taking action against, an owner whose dog is allowed to bark excessively. Your council may require more than one complaint to progress an investigation. Your council may require you to keep a log of when, and for how long, the dog is barking.
Talk to neighbours to see if they share your concerns. If they do, encourage them to write to the local council too. Having multiple complaints enables your local council to make a stronger case for action to be taken and ensures that it has the appropriate standard of evidence to prove a case in court, if required.
If your local council identifies a serious or ongoing problem, it may issue a nuisance order requiring the owner to prevent the dog barking.
You may also wish to consider taking independent legal action by seeking a noise abatement order under the Protection of the Environment Operations Act 1997 through your local court.