And how does the process work?
A dispute between the Steam Packet Company and maritime trade union Nautilus continues to rumble on.
The latest announcement came yesterday (17 November) which gave notice of the union's intention to ballot members for industrial action.
It comes amid a lengthy dispute spanning two and a half years, with claims of 'fire and rehire', 'non-negotiable' terms and discussions said to have reached an 'impasse'.
A period of seven days' notice is given by the union before ballot papers are expected to be sent out which will ask if members are in favour of taking action, and to what extent.
It's not yet been confirmed when workers are likely to stage industrial action, but what we do know is that both strike and action short of strike will be on the ballot paper, as Garry Elliot - Senior National Organiser for Nautilus - explains:
The Steam Packet Company insists it's open to talks and urges the union to come to the table rather than 'threatening disruption of lifeline services', but it maintains the 'live on board' model is a 'fundamental, contractual' requirement of future employment.
However, the Steam Packet does say "officers with circumstances requiring them to be at home on a daily basis will be accommodated as far as possible."