Article 49 stipulates that an accounting period typically ends twelve months after its start. However, if a business ceases (in the case of establishments, PEs, or joint ventures) or if an Omani company is liquidated before the twelve-month mark, the accounting period ends on the date of cessation or conclusion of liquidation. This rule ensures that the final tax return for a closing entity covers exactly the duration of its operations in its final year, preventing the requirement to report for a 'ghost' period after business has ended.