The popularity of rental platform Airbnb and a rise in the volume of social influencers have led to a surge in the number of people who have to make a self-assessed tax return.
A crackdown by Revenue to enforce tax compliance is also being cited for a big rise in the number who will have to pay tax on self-employed income by the end of this month.
The number of people who now file a self-assessed tax return has shot up by 112,000 in the last five years. Some 730,000 are expected to file a tax return this year, according to Taxback.com.
The growth in what is called the 'sharing economy' has been a big contributor to the rise in the number who are now classed as self-employed, CEO of Taxback.com Joanna Murphy said.
She said: "Ireland's sharing economy has exploded in recent years through activities such as Airbnb, which has become a significant income generator for a growing number of people, some of whom have made a full-time business from hosting via the platform.
"In addition, Instagram has facilitated the development of whole new entrepreneurial sectors and new income streams for influencers, who can earn an income promoting products and services online for big brands."
She said stringent enforcement of tax compliance by Revenue was another significant contributing factor to the growth in the number of new registrations on ROS (Revenue Online Service).
This means there is much greater awareness of tax compliance among the public. "The focused clampdown of Revenue on non-compliance throughout the country has had a significant impact in recent years," Ms Murphy said.
The tax deadline for self-assessed taxpayers is October 31. Those filing and paying online have until November 12.
The tax expert said the addition of "self-assessed newbies" every year brings with it a greater chance for deadlines to be missed.
Ms Murphy said that any income people earn is most likely taxable and reportable, and must be declared to Revenue.
"If people do find themselves with additional income, perhaps outside of their PAYE employment, they are required to file a tax return," she added.
Anyone who earns more than €5,000 net untaxed a year will need to register as a self-assessed individual by completing a TR1 form. People will then need to file a Form 11 tax return and make a tax payment by October 31 each year for the previous year's earnings.