A shake-up of overtime and public holiday conditions could be looming amid a sweeping review of workplace deals covering more than a million Australians.

Big business is pushing for modern-award provisions for workers to surrender overtime pay and instead get time off, while the union representing the nation's retail staff wants workers to get a day off when a public holiday falls outside their five-day week.

Big business wants provisions for workers to get time off instead of overtime pay... Credit:Paul Rovere

The submissions have been lodged with the Fair Work Commission, which is reviewing pay and conditions across the 122 modern awards that cover many Australian workers.

The Australian Industry Group says clauses allowing for "time off in lieu of payment for overtime" were critical to provide businesses with much-needed flexibility.