No Longer the Same, What Are the Key Changes in Filing Individual Income Tax Returns in the Coretax Era?

The implementation of the Core Tax Administration System (Coretax) marks a new chapter in Indonesia’s tax administration. One of the most noticeable changes for the public is the transformation in the filing of Individual Income Tax Returns (IITR), both in terms of format, data completeness, and the level of detail required. Following the implementation of Coretax, IITR must be filed electronically, with the filing guidelines referring to Appendix G of the Directorate General of Taxation Regulation Number PER-11/PJ/2025.

Changes in Filing Forms

Prior to the implementation of Coretax, IITR were categorized into several types of forms, namely Form 1770, 1770 S, and 1770 SS. In practice, this classification often caused confusion, particularly for taxpayers whose economic circumstances changed from year to year. Through the implementation of Coretax, this separation of forms has been eliminated and replaced with a single integrated IITR reporting system. Taxpayers no longer select a form type at the beginning, instead they input data according to their income conditions. The system automatically adjusts the structure and data entry fields based on the information provided. In addition, unlike the previous DJP Online system which still allowed offline filing through e-Form, Coretax now requires an active internet connection throughout the reporting process. Nevertheless, the IITR does not have to be completed in a single session, as Coretax provides a draft saving feature that allows taxpayers to temporarily save their data. This feature minimizes the risk of data loss in case of internet disruption and offers flexibility for taxpayers to complete their filing gradually.

Prepopulated Data

One of the most significant features of Coretax is the prepopulated data mechanism. When an individual taxpayer begins to fill out the IITR, certain information automatically appears in the system. This includes taxpayer identity data such as National Identification Number, name, email address, phone number, family data (in accordance with the Family Tax Unit in the Coretax profile), asset data based on the previous year’s return, withholding or collection tax slips issued by third parties, income tax payment data, and Income Tax Article 25 installments. This feature minimizes the risk of input errors, omitted data, and discrepancies in tax credits. Taxpayers are only required to verify the information before submitting the IITR. If any withholding slip is inaccurate, the system provides a direct deletion feature.

Automated Validation of NPPN

Under the previous system, the use of the Net Income Calculation Norm (NPPN) through e-Form was relatively more flexible in practice. Taxpayers could fill in the norm column and input a certain percentage even if they had not officially submitted a notification to the Directorate General of Taxes (DGT). The system did not automatically verify the existence of such notification at the time of filing. As a result, in some cases, the use of NPPN relied more on the taxpayer’s awareness and understanding of the applicable formal requirements. This situation has changed significantly in the Coretax era. The system no longer allows flexibility without validation. When a taxpayer selects the NPPN calculation method, Coretax immediately checks the DGT database to confirm the existence of a valid NPPN notification. If no valid notification is found, the norm field is automatically locked and cannot be completed. From a tax governance perspective, this measure strengthens legal certainty and ensures that tax facilities are only utilized by taxpayers who administratively qualify. From the taxpayer’s perspective, this change requires greater administrative compliance and careful planning from the beginning of the tax year. If a taxpayer intends to apply the NPPN method, they must ensure that the notification of NPPN usage has been duly submitted and properly recorded in the DGT database before the relevant tax year begins.

Reporting Becomes More Detailed

Referring to Appendix PER-11/PJ/2025, there are significant changes in the format of asset and liability reporting in the IITR under the Coretax system. Previously, taxpayers were only required to report the acquisition cost of their assets, and all types of assets were presented in a single table. Under the new provisions, taxpayers must also disclose the current value of their assets, and the reporting is now divided into seven separate tables, namely cash and cash equivalents, receivables, investments or securities, movable assets, immovable assets, other assets, and an asset summary. Each category has a more detailed format and specific columns according to the characteristics of the asset. For example, in the immovable assets section (land and/or buildings), taxpayers must provide information such as certificate number, source of ownership, and property size. For movable assets such as motor vehicles, taxpayers are required to state the license plate number, ownership status, and include the type and brand in the description column. Liability disclosure has also been adjusted. Taxpayers must now provide the identity of the lender, such as the National Identification Number or Tax Identification Number. In addition to assets and liabilities, income reporting has also become more detailed. Income subject to Final Income Tax as well as non-taxable income must now be reported by stating the identity of the Tax Withholder or Income Payer, including their National Identification Number or Tax Identification Number. As a result, the reporting system becomes more structured and specific.

Payment of Underpaid Income Tax

In cases where the IITR results in an underpaid status, the payment mechanism has also changed. Under the previous system, taxpayers were required to generate a billing code before making payment. Through Coretax, this process is directly integrated into the tax return filing workflow. The billing code is automatically generated when the taxpayer selects the pay and file option, eliminating the need to create the billing code separately. In addition, any tax underpayment may be settled using the available tax deposit balance, under tax account code and tax payment type code 411618-100.

This concludes our overview of Coretax for Individual Income Tax filing. For readers who require assistance in filing their Income Tax Return through Coretax, please contact us at DSH Tax Consulting.

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