Your contract of employment may contain clear written terms detailing other authorised absences for which you may be paid. Details will be in your contract, or in the written statement of particulars which sets out your terms and conditions of employment. Your employer must provide you with this written statement within a month of starting work. (From April 2020, your employer will have to give you this statement from the first day of your job.)
Other absences count as unauthorised absence. An employer is generally entitled to deduct wages for unauthorised absence.