People are being warned about the cost of buying from UK-based websites is going to rise from January.
Ordering €152 worth of clothes from the UK could end up costing as much as €236 when delivery, VAT and customs are accounted for post-Brexit.
There will be no difference when buying less than €22 worth of goods until July 2021.
Ray Ryan, from the Brexit unit of the Revenue Commissioners, says orders above that amount will incur extra charges.
He said: "When you go to the €150 level, customs and VAT are payable when buying something for more than €150.
"The value of goods at that stage is actually excluding the shipping, delivery, insurance and handling charges, once that's over €150 that's when customs usually come into play."
An email sent to Amazon customers in Ireland this week, meanwhile, warned that packages may be subject to "custom duties, taxes and import fees".
Speaking on The Hard Shoulder, tech correspondent Jess Kelly explained: "This could result in you going to buy something on Amazon, seeing it for €30, and then all of a sudden there's anywhere from €10, €20 to €30 added on.
"This email has naturally enough caused quite a few questions."
It comes not long after the arrival of Amazon Prime in Ireland, and Jess said it's not yet clear whether Prime customers here will face a price hike or any impact to delivery speeds as a result of the imminent changes.
She also pointed to the impact Brexit has had on Revolut, who are moving Irish customer accounts from the UK to Lithuania while it awaits an Irish banking licence.
She observed: "We are in for so many headaches as this comes through... we are going to get millions of these emails from companies."
Brexit talks
It comes as the British Prime Minister travels to Brussels this evening to meet with the European Commission President to hold Brexit talks.
An evening dinner between Boris Johnson and Ursula von der Leyen will try to break the impasse reached by negotiators.
A three-course dinner with a side of diplomacy will be on the cards and the two leaders will decide whether there's any point keeping the trade negotiations going.
Negotiators Michel Barnier and David Frost seemingly having run out of road this week, with key differences remaining between the EU and UK on fishing and the level playing field.
Earlier today, Foreign Affairs Minister Simon Coveney said he doesn't believe the current deadline of the end of the year can be moved.
He said an extension of the process is "very unlikely" and that "the EU has really had enough of this".
However, the Tánaiste Leo Varadkar was more optimistic and said he believes a Brexit trade deal can still be reached in the coming days.
Reporting by Seán Defoe and Stephen McNeice
