The workplace tribunal has rejected the retail union's push to delay cuts to Sunday rates and align them with the delayed minimum wage increase, citing uncertainty over the economic outlook from the coronavirus crisis.

The Fair Work Commission late Wednesday held the Shop Distributive and Allied Employees Association's (SDA) alleged link between the phased cuts to penalty rates and annual wage rises was "not as strong" as the union claimed and so refused to delay them until February 2021 when minimum wages will lift for retail.