Kaj Hoffren, Senior Adviser at the Finnish Tax Administration, says that up to 300,000 taxpayers in Finland have erroneously received tax cards with the wrong tax rate. Newspaper Helsingin Sanomat first reported the mistake on Wednesday.
Hoffren said a software update carried out in the spring of last year was to blame for the error, saying that the computer programme had been using 2015 data to calculate the rate for this year's cards, rather than 2016.
Officials reportedly already noticed late last year that a small number of erroneous tax cards had been sent out.
Every adult in Finland is sent a tax card around the beginning of the year. Taxpayers then send the cards to their employers, ensuring that the right amount of tax is withdrawn from paycheques.
Having the correct income tax rate, in relation to salaries is important; if the rate is too high, too much money is unnecessarily withheld - and if the rate is too low, taxpayers are forced to pay back taxes at the end of the year.
Taxpayers asked to determine correct tax rate themselves, online
The agency says it does not plan to send out new tax cards to those affected, but is sending out letters with information about how to go about determining the correct rate - and how to obtain a new, correct tax card online.
The agency adds that it is possible to call or visit local tax offices around the country to remedy the issue, but said offices have recently been very busy assisting tens of thousands of people asking about this year's tax cards, also before the announcement about the mistake was made. On Tuesday alone, some 64,000 people called tax offices.
Most of the erroneous tax cards - with too low tax rates - were sent to the unemployed, those who receive sickness allowances or parental benefits recipients.
In a press release on the matter, the tax authority noted that 2017's income tax rates would be going down by one to one-and-a-half percent, explaining that a lower tax rate on this year's card doesn't necessarily mean the card is inaccurate.
