You are entitled to tax credits depending on your personal circumstances, e.g. married person's tax credit, employee (PAYE) tax credit, etc. These tax credits are used to reduce the tax calculated on your gross pay. Tax credits are non-refundable. However, any unused tax credits in a pay week or month are carried forward to subsequent pay period(s) within the tax year.
Guide Dog Allowance
Tax Relief Chart
PAYE Credits
Dependant Relative Credit