Any days worked over 14 offshore are paid at time and a half as we work a 2 weeks on, 2 weeks off equal time rota. Our overtime rate is based on our basic wage as time and a half.
If the pay rise was officially introduced to start from 1 June and the employer backdated your normal pay to that date, what you are entitled in terms of overtime will depend on how that pay is calculated. If the overtime pay was calculated separately to your normal pay then it is most likely that it would be treated as a separate payment and not subject to the increase unless the employer agrees to include it. However, if it was directly based on your basic pay, for example by using a calculation which is directly linked o your basic pay then you can indeed argue that this pay should be backdated as well. The key issue here really is - is the overtime directly linked to the basic pay you receive, because if it is then it should be backdated as well.
In order to try and resolve this, the employer should be contacted in writing, advised that this is being treated as unlawful deduction of wages and ask them to pay back the money within 7 days. Also state that if they fail to pay the money that is owed, legal proceedings could follow.
If the employer does not return the money as requested, the following options are available:
Hopefully by taking any of these steps the employer will be prompted to reconsider their position and try to resolve this without having to take the matter any further. Also if there are a number of you affected, you should pursue this as a group rather than individually as that should place more pressure on the employer.
I hope this has answered your query. Please take a second to leave a positive rating, or if you are unhappy for some reason with the advice - please get back to me and I will assist further as best as I can. Thank you very much