Top 10 Common Mistakes in Personal Income Tax Returns: You Could Lose Money

Preparing a personal income tax (PIT) return has become significantly simpler, yet many taxpayers still make errors that can result in delays or financial losses. According to Niveus, the most frequent issues include accepting the draft tax return without verification, failing to claim all eligible tax reliefs, and incorrect handling of multiple income sources or special personal circumstances. A few minutes of thorough review and adherence to key administrative steps can substantially reduce the risk of errors and subsequent corrections.

Niveus has compiled the most common mistakes to watch out for during the 2025 tax filing period.

1. Automatic acceptance of the draft tax return without verification

Many taxpayers assume that the draft prepared by the National Tax and Customs Administration (NAV) – available from 15 March – contains all relevant data. However, this is not always the case. Income from real estate rentals, foreign sources, or certain unreported investments is frequently missing.

2. Failure to claim eligible tax reliefs

A common error is not utilising all available tax allowances – such as the family tax allowance, newlyweds’ allowance, or personal allowance – resulting in the loss of potentially significant refunds.

3. Incorrectly reported or omitted income

Irregular income streams – for example, from occasional work, foreign employment, or certain investment activities – are often overlooked or incorrectly declared.

4. Incorrect bank account number provided

A surprisingly frequent administrative mistake is entering an erroneous bank account number for the tax refund, which can delay payment.

5. Ignoring filing deadlines

Many taxpayers leave submission until the last minute, increasing the likelihood of errors and administrative complications.

6. Incorrect handling of income from multiple employers

In cases of job changes or concurrent employment, discrepancies between withheld tax and actual liability frequently arise. It is therefore essential to cross-check employer certificates.

7. Incorrect accounting of real estate sales

The taxation of income derived from the sale of real estate is subject to complex rules; therefore, it is often reported incorrectly or incompletely in tax returns, or in some cases not considered at all.

8. Overlooking sole-trader status

Sole traders’ returns are significantly more complex, and errors in cost accounting can easily lead to differences between declared and actual tax obligations.

9. Failure to designate or incorrect designation of the 1+1%

Many taxpayers forget that the 1+1% tax allocation must be made separately, or they fail to indicate the correct beneficiaries.

10. Ignoring employer certificates (e.g. M30)

Failure to review employer-issued certificates can result in an incomplete or inaccurate tax return.

Conscious verification is key 

“Digitalisation has greatly simplified tax filing, but ultimate responsibility still rests with the taxpayer. A few minutes of careful checking can prevent serious inconvenience and financial losses.” emphasised Lajos Bagdi, Partner at Niveus.

Checklist for Reviewing Your Tax Return 

• Review every item in the NAV draft return – do not accept it automatically 
• Cross-check employer certificates (M30) against the draft 
• Collect all supporting documents for every income type (foreign, real estate, investment, etc.) 
• Verify that all eligible tax reliefs have been claimed 
• Double-check the bank account number and personal data for typos 
• Pay particular attention to discrepancies when multiple employers are involved 
• If you sold real estate or had business income, carefully review the specific rules 
• Do not leave submission until the last minute 
• Designate the 1+1% tax allocation 
• In case of doubt, seek professional advice 
• Taxpayers in special situations (foreign employment, multiple income types, business activity) should conduct a particularly detailed review or consult a tax expert.