Consider the tax treatment of both the $500 and $2,000 amounts by Anna

Anna is an accountant who owns a small business advisory firm in town. She has a rental received property and an agent leases this property on her behalf. This year she calls her agent to enquire about the rent she received. After some investigations, the agent realised she had been underpaid an amount of $500. The agent pays her this amount and in addition to this, the agent offers Anna a once off payment of $2,000 if she agrees not to disclose any information about the underpayment to anyone. Anna agrees and receives both the $500 and the $2,000.