Extra charges will apply for anyone shopping from UK based websites from the 1st of January next year.
The government's Brexit preparations plan warns import charges, duty and VAT costs will apply similar to when ordering from the US or China.
It means people will have to pay more for any goods ordered from the UK when they arrive.
The government plan is warning all businesses trading to, from or through the UK to prepare and has announced some financial supports for dealing with extra customs costs.
Yesterday the British government admitted it was willing to break international law and the Withdrawal Agreement if there's no trade deal.
Later today, Micheál Martin and Boris Johnson will speak over the phone with the Taoiseach saying he will raise Ireland's complete opposition to the UK's attempt to undermine the Brexit agreement.