Before you start

Know your residence position: more than 182 days in Cambodia in a 12-month period makes you a resident
An employer registered with the General Department of Taxation who operates Tax on Salary withholding
Records of any income you receive from outside Cambodia
Awareness of your home country's rules — Cambodia's treaty network is thin

Step-by-step

1
Work out whether you are a Cambodian tax resident
You are resident if you are domiciled here, have your principal place of abode here, or are present for more than 182 days in a 12-month period. Note the framing: 182 days in a rolling 12 months, not in a calendar year, so a stay straddling New Year can make you resident in a way a calendar test would not.
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2
Let your employer withhold Tax on Salary monthly
Registered employers calculate and remit Tax on Salary each month. Resident employees pay progressive rates on monthly salary, rising through 5%, 10% and 15% to a top rate of 20%. Non-residents pay a flat 20% on Cambodian-sourced salary, and for them that is a final tax.
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3
Check how your benefits are being treated
Fringe benefits — housing, a car, school fees, allowances — are taxed separately at a flat 20% on their value, and the tax is borne by the employer. Packages here are often quoted with accommodation included, so ask HR in writing how each element is being taxed before you sign.
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4
Account for income from outside Cambodia
Under the Law on Taxation a Cambodian resident's salary is assessable whether it is Cambodian- or foreign-sourced, while a non-resident is taxed only on Cambodian-source salary. Enforcement against foreign-source income has historically been light, but light enforcement is not a rule, and it is not something to rely on. Take Cambodian advice if a meaningful part of your income arrives from abroad.
OnlineWho: You (with an adviser)Before your first full tax yearAdviser's fee
5
Handle your home-country obligations separately
Cambodia has relatively few double-taxation agreements compared with Thailand or Vietnam, so relief you might expect elsewhere may simply not exist. Check whether your own country has a treaty with Cambodia before assuming a credit is available.
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Documents you’ll need

Passport and entry/exit stamps — your day count is your evidence
Employment contract showing salary and benefits
Monthly payslips showing Tax on Salary withheld
NSSF deduction records
Records of any foreign-sourced income and tax paid abroad

Things most newcomers don’t know

The 182-day test runs on a rolling 12 months, not the calendar year.

Cambodia's residence test is more than 182 days in any 12-month period, which is a different question from 'more than half of this calendar year'. Someone who arrives in September and stays through the following summer can be resident on the rolling test while a calendar-year count would say no. If you are near the line, count forwards and backwards, not just from 1 January.

Source: PwC Worldwide Tax Summaries — Cambodia residence

Non-resident is not the cheap option here — it is a flat 20% from the first dollar.

In many countries non-residence means a narrower tax base. In Cambodia it means a flat 20% final tax on Cambodian-source salary with no progressive bands and no threshold, while a resident on a modest salary pays 0% on the first 1,500,000 riel a month and single-digit effective rates well up the scale. For most salaried people, becoming resident reduces the bill rather than increasing it.

Source: PwC Worldwide Tax Summaries; Cambodian Law on Taxation

There is no annual personal return, which is why mistakes persist.

Because Tax on Salary is withheld monthly and a plain employee never files anything, nothing in the calendar forces you to check whether your residence status, your benefits treatment or your foreign income has been handled correctly. Errors compound quietly for years. Schedule your own annual review even though the state does not ask for one.

Source: General Department of Taxation; Acclime Cambodia

Cambodia's double-tax treaty network is thin — check before assuming relief.

Cambodia has signed far fewer double-taxation agreements than its neighbours, and many Western countries are not among them. That means income taxed here may not generate a credit at home, or vice versa, and the usual assumption that a treaty will smooth things over does not hold. Verify your specific country pair rather than reasoning from how Thailand or Vietnam works.

Source: General Department of Taxation treaty list

Common mistakes to avoid

Counting the 182 days against the calendar year instead of a rolling 12 months
Assuming non-residence is cheaper — it is a flat 20% final tax with no threshold
Not asking how housing and school-fee benefits are being taxed before signing an offer
Assuming a double-tax treaty exists between Cambodia and your home country
Treating light enforcement on foreign-source income as if it were a legal exemption
Relying on this guide instead of a Cambodian tax adviser once your position is anything but a plain salary

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.