If you will be staying in Finland for a maximum of 6 months and your employer is a Finnish company, you will pay Finnish withholding tax at a rate of 35%, which the employer will deduct from your wage. Before this, the employer may deduct 17 euros/day from your wage. This deduction must be recorded on a tax-at-source card, which is given by the tax office.
In addition to tax, the employer will withhold social security and insurance contributions from your wage (total about 7%), unless you have the E 101 certificate, which shows that you are insured outside Finland. The withholding tax is the final tax and a tax return is generally not needed in Finland.
You must obtain a Finnish personal identity code from the local register office.The tax-at-source card application form VEROH 6201 and instructions on applying for a personal identity code can be obtained from a tax office in Finland. Give the tax-at-source card to your employer. When your employment comes to an end, your employer will be obliged to give you a certificate showing the income you have received and the withholding tax collected from you. Keep this certificate because, if necessary, you will be able to show it to the tax authorities in your country of residence.
If your pay in Finland constitutes 75% or more of your total annual gross earned income and you are a resident of an EEA country, you can (after the income year) ask for progressive taxation instead of the flat 35-percent tax. Use form VEROH 6148 to present this claim after the income year is over.
If you will be staying in Finland for a maximum of 6 months and you will be receiving a wage from other than a Finnish employer, you will not have to pay tax on your wage in Finland. You will submit a tax return and pay taxes only in your home country. A foreign company that has a permanent establishment in Finland is looked on as Finnish company for tax purposes. If a foreign employer has a permanent establishment in Finland, the wage received from this employer is always taxed in Finland.
Further information is available on the Finnish Tax Administration’s website