Legislation that bans absolutely no hour contracts passed its 3rd and final reading in Parliament last month.
The modifications mean employers will have to ensure hours and provide sensible payment to employees for being available.
Businesses have up to 12 months making modifications to the agreements, which influence tens of thousands of workers.
Unite union’s national secretary Gerard Hehir said companies would not get away with ensuring one hour or providing just a few cents in payment.
“It’s going to have to be sensible, you know it’s not going to be a few cents or a totally free meal or a pat on the back. It’s going to have to be something the company makes sure the worker is reasonably made up for the fact that week by week they do not know the number of hours they are working or when they are working.”.