It will be necessary to decide whether you propose to trade as a Sole Trader/Partnership or as a Limited Liability Company.
Branches of a UK company must be registered with the Companies Registration Office. The registration must take place within one month of setting up the branch, by submitting a Form 12 along with the necessary documentation. For more details, please refer to information leaflet no 5 registration of external companies at www.cro.ie.
It is important to ensure that when making the submission to the CRO that the company Memorandum and Articles of Association of the UK Company are certified to be a true copy of the original by a Notary Public or by the registrar companies from the country that the company was incorporated.