What are 'premium/differential' payments based on?

Premium or differential payments typically arise from collective agreements, which may outline specific conditions under which employees receive additional compensation for certain hours worked. These agreements can include provisions for things like overtime pay, shift differentials for working less desirable hours, or pay enhancements for specific qualifications or certifications. This means that such payments are often negotiated terms of employment rather than being contingent on individual performance or the nature of a position.

In contrast, the other options refer to different compensation components that do not specifically relate to additional payments for particular work conditions set out in collective agreements. Highly skilled positions might command higher salaries generally, but that isn't the same as a premium payment defined in collective agreements. Employee performance reviews often inform raises or bonuses, but are not typically the basis for premium payments. Annual salary adjustments are set to align with cost of living or company performance rather than tied specifically to the working conditions that differential payments address.