GPs are often requested to give hepatitis B immunisation covering three broad areas:
– for travel
– for occupational health
– for medical reasons (e.g. IV drug use for renal disease.)
Hepatitis B immunisation for travel is not remunerated by the NHS as part of additional services.
Schedule 5 of The NHS (General Medical Services Contracts) Regulations 2004 of states that:  
“The contractor may demand or accept a fee or other remuneration…. for treatment consisting of an immunisation for which no remuneration is payable by the Primary Care Trust and which is requested in connection with travel abroad”  
Technically the practice may charge any patient a private fee for hepatitis B for travel, as long as it is not combined with hepatitis A, which must be given on the NHS.
Ultimately it is up to the practice to decide when and if it is clinically appropriate to use the combined immunisation, such as where there is high risk of infection or a barrier to compliance.
Practices therefore need to be clear about their policy to avoid falling foul of regulations that prohibit charging NHS registered patients.
The service must be provided either entirely as an NHS process or entirely as a private service.
Occupational health
There is no obligation under the GMS regulations for a practice to provide occupational health services for patients. That responsibility rests with the employer under Health and Safety Legislation, and in occupations where there is a risk to health from any form of work related infection it is the employer’s duty to assess that risk and, if present, to protect the workforce.
The same applies for healthcare students who often request a hepatitis B immunisation prior to, or on entering, a course.
Medical Schools are legally responsible for providing a full occupational health service to their students and applicants.
It is worth noting that a practice can choose to enter into a private contract with an employer or medical school to provide this service, either to a group of employees or for a single employee.  If a practice decides to enter into a contract to provide such a service, it cannot accept a fee from the registered patients, only from the employer.
Note that practices cannot under any circumstances charge their NHS patients for the occupational service or the hepatitis B vaccine provision.

Lifestyle risk or medical conditions (or ‘patients at risk’)
Certain lifestyles will put some people at more risk of infection and practices can only act upon patients giving the information. Examples of this may include tattoo parlour workers (difficulty arises from self-employed tattoo parlour owner versus occupational health aspects of employee working), or family members of intravenous drug users and prostitutes.
Giving hepatitis B for those at lifestyle or medical risk is not part of the GMS contract.  

Practices are only obliged to offer this service as part of good medical practice and therefore under GMS in clinically appropriate situations, which are determined on an individual basis.