You can claim tax relief on costs for attending a professional seminar. This includes the registration cost as well as any other costs that are directly linked to attending the seminar. For example, travel, accommodation and subsistence.
However, if you combine a seminar trip with a personal excursion (as in a holiday) unless you can clearly separate the business costs from the non-business costs then you will not be able to claim any of the costs.
Professional subscription costs can be claimed for tax relief as long as the membership of the society or institute allow you to use a qualification and you use that qualification for your business. For example an HR Manager can claim their membership cost for the Chartered Institute of Personal Development (CIPD).
You can also claim tax relief on other subscriptions, for example membership of the local Chamber of Commerce, as long as they are solely used for business purposes.