If there is no written employment contract, you may write-up--or otherwise discipline; up to and including terminating--the employee at any time, for any reason (including non-business related) which is not illegal discrimination (e.g. against the employee due to race, religion, age over 40, sex, or disability), not retaliation for reporting discrimination, not for refusing to violate the law, and not retaliation for reporting a violation of the law. If there is an employment contract, follow its provisions in regard to write ups and discipline.An employer may not deny pay to any employee unless 1) required by law (e.g. FICA withholding; wage garnishment per court order) or 2) is consented or agreed to by the employee (e.g. voluntary repayment of amounts borrowed from the employer, or withholding for health insurance or 401k). If the business owner believes the employee intentionally or negligently (unreasonably carelessly) cost it money, the employer could sue the employee to recover that money.