Consumer experts have urged online shoppers not to be duped by '.ie' websites not based in Ireland or they could face additional taxes and duties on what they buy.
It comes post-Brexit and a month after the EU-UK withdrawal agreement became operational.
The European Consumer Centre (ECC) said people need to be aware whether the online shops they are buying from are based in Europe or outside it.
It warned not all '.ie' websites are hosted in Ireland, resulting in Irish online shoppers being hit with additional fees when their purchases were delivered to their doors.
"'.ie' doesn't guarantee that the trader is based here in Ireland," ECC Director Dr Cyril Sullivan told RTÉ's Morning Ireland.
The UK's exit from the European Union means it no longer benefits from the single market. Its exports, excluding those from Northern Ireland, now face taxes like any other goods imported in to the EU from other parts of the world.
The Office of the Revenue Commissioners has clear guidelines.
In a statement it explained: "Irish consumers need to be aware when buying goods from the UK (excluding Northern Ireland) that they may have to pay certain taxes and duties such as VAT, Customs Duty and Excise Duty. Whether or not these additional charges arise depends on the value, type and origin of the goods being purchased".
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Anne Gunnell, director of tax policy at the Irish Tax Institute, explained that this means a customs value (including cost, transport, insurance and handling charges) of €22 or less, will have no additional import charges.
A customs value of more than €22, will mean the consumer will have to pay VAT, while an intrinsic value (the value of the goods alone excluding transport, insurance and handling charges) of more than €150, means the consumer may have to pay both VAT and Customs Duty.
On top of this, the postal service or courier company delivering the goods completes relevant customs declarations. The consumer must pay any additional charges to the postal service or courier company before the goods are delivered.
An Post tells customers about those charges by pushing out a notification by post, text message or email.
"If a charge arises we will send a message - if customs have raised a charge - to the customer with options to either go to their local post office or to go online. When that charge is then paid we will deliver the item," Director of International Mail with An Post Cyril McGrane, said.
Delivery company DPD also looks for payment in advance before they release a parcel in these circumstances.
Its CEO Des Travers said some customers are not happy and there is a bounce in the domestic delivery market.
"About 25% of customers haven't paid the amount of money that is requested of them. Another 25% are waiting for up to three days before they actually pay the amount of money that is due. If you don't pay, your parcel goes back to the sender," Mr Travers said.
He added that from the deliveries it sees since the withdrawal agreement became operational, more Irish customers are shopping on domestic websites rather than British ones.
The ECC has a number of tips for people shopping online post-Brexit.
They include shopping on a secure website, using a credit card or payment companies like PayPal so transactions can be traced if there is a problem after purchase, seeing if there are duties and taxes at the point of payment, and making sure the website is in the EU or outside it.
The ECC had 400 complaints this year and half are associated with changes linked to Brexit.
"We have received around 400 complaints. In or around 50% of those relate to UK traders. Approximately 100 of those relate to Brexit issues," Dr Sullivan said.
He stressed people need to be aware of where the website they are buying from is based as some '.ie' addresses are outside the EU.
He said the ECC had received complaints about such websites after people were charged extra taxes and charges.
"On top of that if there are returns to be done you then have to pay for returns. If there is a large item delivered to your house, and you have to incur costs as part of the terms and conditions, in terms of the transaction you could find yourself heavily hit," he said.