Things like this often happen to taxpayers who are employees of two or more employers in one tax year.
The cause of this underpayment is the calculation of Non-Taxable Income (PTKP) which is done more than once, namely when each employer makes deductions. Meanwhile, for one taxpayer, in calculating income tax (PPh), PTKP can only be calculated once.
Is the employer wrong? No, if the taxpayer is indeed an employee of the employer. In accordance with the Article 21 withholding income tax provisions for employees, employers should have taken into account the PTKP when calculating the amount of income tax that must be withheld.
As for the income of taxpayers from other employers, it has nothing to do with the income paid by the first employer so that each is independent in making deductions.
Given that the Indonesian taxation system is a self-assessment, in which the taxpayer is required to calculate his own income and income tax, the taxpayer recalculates all income he receives in that year along with his income tax.
Income is the total of all income earned during a tax year, not just from one employer, so that when recalculated, there is a potential for underpaid taxes and must be paid by the taxpayer himself before submitting his Annual SPT.