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When they informed BigBoss of their decision, the promised bonus summarily disappeared and they were told, since they were leaving, they effectively forfeited their right to the bonus.
The only trouble is that they were already sent an agreement for the additional cash, which had been signed and approved. When OP reminded BigBoss of this, they were essentially told to lawyer up.
Source: https://www.distractify.com/p/hr-director-attorney-bluff-called
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