Just one in 100 people is claiming back flat-rate expenses from the Revenue every year, according to Taxback.com.
The tax advisory firm said thousands of workers are missing out on hundreds of euro by not claiming the expenses.
Flat-rate expense allowances are available to workers based solely on their occupation – allowing them to claim back money spent on clothing, equipment or other essential items.
The money can be claimed directly back from Revenue with no need to send in receipts or other documents.
On Newstalk Breakfast this morning, Taxback.com spokesperson Marian Ryan workers are leaving "a huge amount" of money on the table.
“There are an awful lot of people not claiming it,” she said.
“It is called a flat-rate expense and basically it is a tax relief you are entitled to based solely on your occupation.
“So, for example, if it is the case you are working in retail as a shop assistant there is a flat-rate expense of €121 a year there.
“There are over 180 different types of flat-rate expenses out there that people are missing out on and from Revenue figures there it looks like about 1% of people are actually claiming their flat-rate expenses.
“There is a huge amount of them left unclaimed out there.”
Ms Ryan said the expenses have not increased in years – and said a review should now be carried to ensure the expenses rise in line with soaring inflation.
“We are calling for them to look at increasing them in line with inflation and maybe broadening the scope of them,” she said.
“There are a lot of employees out there that aren’t entitled to flat-rate expenses.”
Ms Ryan said claiming the expenses once will see you handed them automatically for as long as you remain in your job.
“Once you work in that specific field, you are entitled to that flat-rate expense and it is just a matter of including it on the tax return there,” she said.
“The beauty of it is that once you claim it once if your occupation or your employer doesn’t change, the Revenue will automatically include it in your tax credit certificate for the following year.
“So not only will you get a refund for the previous four years for any tax paid. You will be paying a little bit less tax going forward as well.”
You can find the full list of flat-rate expense allowances here.
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