The number of people who declared income earned via these platforms also jumped from 69 to 319.

"The increase in both numbers shows that when a simple service is available, people tend to prefer to fulfill their tax obligation and thus make a contribution to society," Hannes Uddde, lead specialist at the Estonian Tax and Customs Board's (MTA) Service Department, said in a press release.

Revenue earned abroad subject to taxation in Estonia was declared in 873 tax returns in an amount exceeding the amount of similar income declared for last year by €8.6 million.

Income from renting a dwelling and other rent income was declared by 1,564 people more than last year, however the sum total subject to taxation declared in their tax returns dropped by €1.5 million.

"Last year, 80 percent of the income earned by renting out a dwelling was subject to taxation, in lieu of the previous 100 percent, which definitely is one of the reasons why there were more people who declared it," Udde noted.

Altogether 685,511 people declared their income for 2016, almost 18,000 people more than the year before. "In previous years, such people had no need to file a tax return because all taxes had been withheld and there were no incentives," the official explained. "This year, filing the tax return on time was one of the conditions for applying for the reimbursement."

The deadline for paying income tax for 2016 and for the reimbursement of the tax paid in excess is July 3. For self-employed persons, individuals who earned income from the sale of property and those who earned income abroad, the deadline is Oct. 2.