Reasons you might need to interact with the income tax system here:
1. You have significant (>€5000) non-employment income.
2. You worked for less than 12 months and are claiming your tax refund.
3. You disagree with the government assessed tax reciept (which is based on what your employer fills in).
For 90% of people then, they don't need to interact with it. Their employer reports their income, deducts an appropriate amount of taxes, and sends it to the government. End of process.
Reasons you might need to interact with the income tax system here:
1. You have significant (>€5000) non-employment income.
2. You worked for less than 12 months and are claiming your tax refund.
3. You disagree with the government assessed tax reciept (which is based on what your employer fills in).
For 90% of people then, they don't need to interact with it. Their employer reports their income, deducts an appropriate amount of taxes, and sends it to the government. End of process.