The Self Assessment System has been introduced to companies since 2001. Under this system, companies are required to determine their own tax liability and make payment to the IRB.

The Self Assessment System has been introduced to companies since 2001. Under this system, companies are required to determine their own tax liability and make payment to the IRB. The process starts with furnishing an estimate of taxable by a company.

Under Self-Assessment System, companies are required to furnish an estimate of its tax payable to IRB for each year of assessment. The estimate is done by filling up a form, namely CP 204. This form has to be be submitted to IRB not later than 30 days before the beginning of the basis period. Upon receiving the completed CP 204 furnished by the company, IRB will then issue Notice of Instalment Payment (CP 205). If a company fails to furnish an estimate by the required date, the Director General of Inland Revenue (DGIR) will issue a direction to the company to make instalment payments. The DGIR may also institute a legal proceeding against the company for the failure to furnish an estimate.

It is important to note that the estimated amount of tax payable for a current year by the company should not be less than the tax estimate to be paid for the immediate preceding year of assessment. However, the company is allowed to revise its original estimate in the sixth month of the basis period for a year of assessment. Following this, the remaining instalment have to be revised accordingly. The application for revision is done using the same prescribed form (CP 204), indicating that it is to provide a "revised estimate". A Notice of Revised Instalement Payment (CP 206) will be issued by IRB to confirm instalment payments following the revised estimate.

If the estimated tax payable is understated (to be known not more than six (6) months after year end), it should be noted that if the difference between the actual tax payable and the estimated tax payable (or the revised estimated tax payable) is more than 30 percent of the actual tax payable,  a 10 percent increase in tax will be imposed on the difference in excess of the 30 percent.