Once IRAS reviews your company’s Form C-S/ Form C-S (Lite)/ Form C, you will receive the Notice of Assessment.

Tax Assessment Process

IRAS adopts a risk-based approach in reviewing the Corporate Income Tax Returns (Form C-S/ Form C-S (Lite)/ Form C) of companies. 

Risk-Based Approach to Tax Assessments

Companies are profiled based on the complexity of their businesses and tax matters, and risk to revenue. This flowchart (PDF, 81KB) illustrates the return review process for companies.

Companies with Straightforward Tax Affairs

Companies with straightforward tax affairs generally do not require detailed reviews of their Form C-S/ Form C-S (Lite)/ Form C on a year-to-year basis. The companies' tax declarations in Form C-S/ Form C-S (Lite)/ Form C are accepted upfront by IRAS with little or no adjustment.

The assessments are completed based on the companies' declarations in the Form C-S/ Form C-S (Lite)/ Form C and Notices of Assessment (Type 4) are issued to the companies by 31 May of the following year.


To complement our risk-based approach, IRAS conducts reviews on a small percentage of companies with straightforward tax affairs by reviewing selected returns under its various compliance programmes.

If your company has been selected, you can expect to receive an enquiry letter from IRAS by 30 Sep of the following year. For example, if your company's Form C-S/ Form C-S (Lite)/ Form C for the Year of Assessment (YA) 2020 has been selected for review, you can expect to receive an enquiry letter by 30 Sep 2021.

The objectives of such checks are to ensure that the Corporate Income Tax Returns filed are complete and accurate and that the assessments are in order. Where necessary, IRAS may request for supporting documents from companies to substantiate their declarations. Amended/ additional Notices of Assessment (Type 4) may also be issued to the companies if tax adjustments are made in the course of such compliance reviews.


Companies with More Complex Tax Affairs

Companies with more complex tax affairs are subject to more in-depth reviews of their yearly Form C-S/ Form C-S (Lite)/ Form C.

Pending the reviews of the Form C-S/ Form C-S (Lite)/ Form C, estimated assessments may be raised based on the companies' declaration in their Form C-S/ Form C-S (Lite)/ Form C.

Such companies can expect to receive the Notices of Estimated Assessment (Type 3) by 28 Feb of the following year. For example, a company with more complex tax affairs, whose Form C-S/ Form C-S (Lite)/ Form C is subject to an in-depth review, can expect to receive a Notice of Estimated Assessment relating to YA 2020, if any, by 28 Feb 2021.

Enquiries and tax adjustments may be made when IRAS reviews the Form C-S/ Form C-S (Lite)/ Form C subsequently. Notices of Assessment (Type 4) are issued to the companies after IRAS reviews the returns. Companies can expect to receive the Notice of Assessment by 30 Nov of the second year. For example, the company can expect to receive the Notice of Assessment for YA 2020 by 30 Nov 2022.

Such companies must still file the Form C-S/ Form C-S (Lite)/ Form C for the following YA by the filing due date of 30 Nov. Prior to receiving the Notice of Assessment, they may file the Form C-S/ Form C-S (Lite)/ Form C based on the last tax position filed with IRAS.

For example, if the company has not received its Notice of Assessment for YA 2020 and wishes to file its Form C-S/ Form C-S (Lite)/ Form C for YA 2021 on 31 Oct 2021 (the YA 2021 filing due date is 30 Nov 2021), it may indicate the amount of unutilised loss items and capital allowances to be brought forward from YA 2020 (if any) based on the YA 2020 tax computation prepared by the company.

After the Notice of Assessment (Type 4 - completed assessment) has been issued, IRAS may review the company's Form C-S/ Form C-S (Lite)/ Form C again should there be new information brought to IRAS' attention. This is subject to the time limit imposed on IRAS with regard to the revision of tax assessments.

Time Limit to Raise Assessments

The statutory time limit for IRAS to raise an assessment or additional assessment is 4 years. However, this statutory time limit does not apply to cases where fraud is involved.

Example 1: Companies with Dec financial year end

Year of Assessment (YA) Financial Year Ending In Statutory time limit to raise an assessment/ additional assessment
2017 2016
(e.g. 1 Jan 2016 to 31 Dec 2016)
31 Dec 2021
2021 2020
(e.g. 1 Jan 2020 to 31 Dec 2020)
31 Dec 2025

Example 2: Companies with non-Dec financial year end

YA Financial Year Ending In Statutory time limit to raise an assessment/ additional assessment
2017 2016
(e.g. 1 Jul 2015 to 30 Jun 2016)
31 Dec 2021
2021 2020
(e.g. 1 Oct 2019 to 30 Sep 2020)
31 Dec 2025

Types of Notice of Assessment

This section summarises the different types of Notice of Assessment issued and whether it is necessary to object to each type of Notice of Assessment.

Type 1: Estimated Chargeable Income (ECI) filed by the company or tax agent

No Notice of Assessment is issued when a nil ECI is filed.

When a positive ECI is filed, the message is as follows:

Sample Message on Notice of Assessment Objection Required?
This is an estimated tax assessment based on the information given by you or your tax agent.

No objection is required.
No

Type 2: ECI raised by IRAS due to failure to file, low ECI declared, or advance assessment

A Notice of Estimated Assessment is issued when ECI is raised by IRAS due to:

  • Failure to file ECI within 3 months from the end of the financial year (excludes cases where the company qualifies for the ECI filing waiver)
  • Failure to file Form C-S/ Form C-S (Lite)/ Form C by the filing deadline
  • Low ECI declared (ECI filed is lower than the tax reported in the Form C-S/ Form C-S (Lite)/ Form C)
  • Advance assessment
Sample Message on Notice of Assessment Objection Required?
This is an estimated tax assessment as we have not received your estimate of chargeable income/ Form C/ Form C-S etc.

If you disagree with the assessment, object via Revise/ Object to Assessment at mytax.iras.gov.sg within 2 months.
Yes, if you do not agree with the tax assessment

Type 3: ECI raised by IRAS based on Form C-S/ Form C-S (Lite)/ Form C filed and pending review

A Notice of Estimated Assessment is issued when ECI is raised by IRAS due to a difference in the ECI declared (Type 1) and the information given in the Form C-S/ Form C-S (Lite)/ Form C.

Sample Message on Notice of Assessment Objection Required?
This is an estimated tax assessment based on the information given in your Form C/ Form C-S.

No objection is required.
No

Type 4: Completed assessment (per Form C-S/ Form C-S (Lite)/ Form C filed by the company or tax agent/ with adjustments by IRAS)

Sample Message on Notice of Assessment Objection Required?
This is your tax assessment.

If you disagree with the assessment, object via Revise/ Object to Assessment at mytax.iras.gov.sg within 2 months.
Yes, if you do not agree with the tax assessment

Objecting to the Notice of Assessment

If you do not agree with your company’s tax assessment raised by IRAS, you may file an objection to have the tax assessment revised.

When & How to File Notice of Objection

Your company must file the objection within 2 months from the date of the Notice of Assessment. If no objection is received within that period, the assessment will be treated as final.

For example, if you receive a Notice of Assessment dated 5 Jan 2021 and do not agree with the assessment, you have up to 5 Mar 2021 to file a Notice of Objection with IRAS.

Go to the Revise/ Object to Assessment digital service at mytax.iras.gov.sg to file your objection.

For assistance on filing a Notice of Objection, refer to these guides:

You will receive an instant acknowledgement.

Notwithstanding any objection, your company must pay the tax stated in the Notice of Assessment within 1 month from the date of the Notice of Assessment.

Objection Process

To ensure timely resolution of objections, the following milestones have been set in the objection process:

1. Request for Information

IRAS may request for information to review objections filed. Your company must reply to these requests by the due dates stated in the request. Where no specific due date is given, reply within 2 months from the date of the letter.

2. Review of Objection

IRAS will review and convey our decision in writing within 6 months from the date of receipt of your last correspondence with complete information. For complex cases where more time is needed to review the tax issue under objection, IRAS will inform you of the estimated time required.

3. Response to Decision

You will be asked to reply in writing whether you agree with our decision on the disputed tax issue by the due date stated in the letter. Where no specific due date is given, reply within 3 months from the date of the letter. If you do not reply by this deadline, the objection will be considered as resolved and closed.

Notice of Refusal to Amend

To ensure objections are addressed and resolved in a timely manner, IRAS may issue a Notice of Refusal to Amend when:

  • Information requested by IRAS remains outstanding after 2 years from the date of receipt of the Notice of Objection.
  • The company does not reply to the decision made by IRAS on the objection (i.e. no response on whether the company agrees or disagrees with the decision) within 3 months from the date of our letter.
  • The company agrees to IRAS' decision but qualifies the agreement with caveat (i.e. the company states that it reserves the right to re-open the case in the event of a favourable decision/ ruling by the Income Tax Board of Review/ High Court/ Court of Appeal).
  • IRAS is unable to reach an agreement with the company on the tax issue under objection.

Learn more about the objection and appeal process (PDF, 898KB).