The default tax year for all registered entities is the calendar year commencing from 1 January to 31 December. However, any registered entity with 51% foreign ownership is allowed to request for new tax year-end different from the calendar year.

Source: https://www2.deloitte.com/content/dam/Deloitte/kh/Documents/tax/kh-tax-guide-to-taxation-in-cambodia-2020.pdf