Hello and thank you for your question.
You have said that the payment is $12,000 plus superannuation for underpayment of penalty rates. Obviously I cannot comment on whether the amount in question is correct or not, however, I do note that the amount you are being offered does not include a superannuation component, which strictly speaking should be paid directly to a superannuation fund. If the money is right but you are receiving funds that ought to be paid to the super fund, then that may result in you being force to pay the amount that reflects the unpaid super to the super fund, so be aware of that possibility.
That issue aside, the release is fairly standard but obliges you to keep the settlement confidential and to have no contact with the employer's clients, staff, contractors or agents, and to attend to any tax liabilities yourself arising out of this late payment (i.e. presumably you should have paid income tax on this money if it had been paid in the first place, and you likely now will be obliged to pay some portion in your return once you declare this new income). These conditions are ones that if you fail to comply with them, the company could sue you to get the money back, so be sure you can comfortably comply with them. In particular, if you have friends who are employees, agents, contractors or clients of this employer, then you either need to cease having contact with them or if you want to maintain the relationship, you should press them to agree that any such restriction is only applicable in the sense that you cannot discuss this settlement with them. Anything beyond that is not a reasonable restriction.
Strictly speaking, if you are confident that you can indeed prove you are entitled to the claimed amount, then you could just proceed with litigation and assuming you win, you will receive the money without any such restrictions, though the reason you may agree to them is to avoid the expense and delay of pursuing your entitlements in court, but if you are really uncomfortable with any particular restriction, you should think twice before simply settling.
I trust the above assists.
If you wish to have a phone call, you can post a request for me tomorrow and I will try to get back to you, but the reality is that experts are not always available on short notice.
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