Generally, tax will be charged on personal earnings (wages, welfare), capital gains, and business  income. The rates for different types of income may vary and some may not be taxed at all. Capital gains may be taxed when realised (e.g. when shares are sold) or when incurred (e.g. when shares appreciate in value). Business income may only be taxed if it is ‘significant’ or based on the manner in which it is paid. Some types of income, such as interest on bank savings, may be considered as personal earnings (similar to wages) or as a realised property gain (similar to selling shares). In some tax systems ‘personal earnings’ may be strictly defined to require that labour, skill, or investment was required (e.g. wages); in others they may be defined broadly to include windfalls (e.g. gambling wins).