Registering a company with Ireland’s Companies Registration Office is only the first part of becoming operational. Once the company is incorporated and begins its business activity, it normally needs to register with Revenue for Corporation Tax and organise its filing, payment and record-keeping obligations.
This guide explains how Corporation Tax registration works in Ireland, what to prepare, when to use ROS or a tax agent, what the Statement of Particulars is, how the tax reference fits into the process, and how to build a first-year deadline calendar. It is written for founders forming an Irish LTD, including founders who live outside Ireland.
Corporation Tax registration in one minute
- Incorporate the company with the CRO and save the Certificate of Incorporation.
- Confirm the company’s activities, trading start date and accounting period.
- Register for Corporation Tax through ROS, a tax agent or the correct Revenue form route.
- Provide the Statement of Particulars within the required period after trading begins.
- Track preliminary tax, the CT1 return, balance payment and any other tax registrations.
These are separate from VAT registration. Read our Irish VAT registration guide if the company will make taxable supplies.
What is Corporation Tax registration?
Corporation Tax registration tells Revenue that the company is within the Corporation Tax system and needs to account for its taxable profits. The company then receives or uses the relevant tax registration details for returns and payments.
Registration does not decide how much tax the company owes. The eventual liability depends on taxable profits, income type, allowable deductions, losses, reliefs and the company’s wider tax facts. A company can be registered correctly and still need a tax adviser to prepare its computation and CT1.
Corporation Tax reference number
After Revenue accepts the registration, keep the company’s Corporation Tax reference details with its CRO number and Certificate of Incorporation. The reference is used when the company or its agent deals with Revenue, files returns and makes payments. It is not the same thing as the CRO company number, VAT number or an individual PPSN.
If the reference details do not arrive, cannot be accessed or do not match the company’s records, resolve that before the first return is due. Do not create a second registration simply because a letter or ROS message is delayed; check the company’s Revenue profile or ask the authorised tax agent to confirm the position.
CRO incorporation is not Revenue registration
The CRO handles the legal formation of the company. Revenue handles tax registrations and tax returns. The company should keep its CRO number and incorporation documents because they are used when setting up its tax profile.
A common mistake is to assume that the CRO automatically registers every tax. It does not. Corporation Tax, VAT, employer PAYE/PRSI and Relevant Contracts Tax are different registrations with different tests. The company should assess each one based on its real activities.
When should a new company register?
A company should organise Corporation Tax registration before or as it begins its taxable business activity. The timing should not be left until the first CT1 deadline. Early registration gives the company time to resolve ROS access, tax-agent authorisation, accounting-period details and any Revenue questions.
Revenue also requires a company incorporated in the State or beginning to trade in the State to provide a Statement of Particulars within 30 days after trading begins. Treat this as an early compliance deadline, not as something that can wait until the annual return.
What to prepare before registration
Have the following information ready before starting the registration:
- Company name, CRO number and registered office address.
- Certificate of Incorporation and constitution details.
- Names, addresses and identity details of directors and the company secretary.
- A clear description of the company’s main business activity.
- Expected date of trading or first taxable activity.
- Accounting period end date and bookkeeping contact.
- Expected turnover, customer location and supplier location where relevant.
- Details of employees, contractors, VAT activity or construction work if other registrations may apply.
- Irish tax-agent details and ROS access information, if an agent will act for the company.
Use a precise business description. “Business” or “online company” is usually less useful than describing what the company actually sells or does, such as software development, marketing consultancy, e-commerce retail or management services.
How to register through ROS or a tax agent
Route 1: your company uses ROS
ROS is Revenue’s online service for business tax administration. A company or authorised person can use it for registrations, returns and payments. The exact screens and access requirements can change, so use the current Revenue instructions and make sure the person submitting the registration is authorised to act for the company.
Route 2: a tax agent registers the company
Many new companies use an accountant or tax agent. The agent can submit the registration and then prepare future returns if the engagement includes Corporation Tax compliance. Confirm what is included: tax registration alone is not the same as bookkeeping, CT1 preparation, VAT returns or annual accounts.
Route 3: the appropriate Revenue form
Revenue provides forms for situations where the online route is not available. An Irish company may use TR2, while certain foreign companies use TR2 (FT). Always check Revenue’s current forms and instructions before submitting, because a form downloaded from an old article may no longer be the correct route.
What is the Statement of Particulars?
The Statement of Particulars gives Revenue information about the company’s trade and tax profile. It is connected with the company’s start of trading, rather than simply the date printed on the Certificate of Incorporation.
The company should be ready to provide the particulars within 30 days after trading begins and notify relevant material changes within the required period. Keep evidence of the trading start date, such as the first invoice, customer contract, platform sale or other commercial record.
Failure to provide the particulars can lead to penalties and may create problems with the company’s status. See Revenue’s current Statement of Particulars guidance for the official requirements.
What happens after registration?
Corporation Tax registration is the beginning of the company’s tax calendar. After registration, the company should:
- Save its Revenue correspondence and tax registration details.
- Confirm the accounting period and bookkeeping process.
- Track preliminary tax requirements and payment dates.
- Prepare the CT1 and any other required returns.
- Pay the balance by the filing deadline.
- Review VAT, PAYE/PRSI and RCT obligations whenever the business model changes.
- Keep company records, invoices and bank reconciliations up to date.
Understanding the 12.5% and 25% rates
Revenue generally applies 12.5% to qualifying trading income and 25% to non-trading or excepted income. Registration does not allow a company to choose the lower rate. The nature of the activity and income determines how the rules apply.
For example, active consulting fees may be trading income, while interest on company cash or rental income may need a separate analysis. If a company has mixed income, the bookkeeping should identify it clearly so the tax computation can apply the appropriate treatment.
Read the full Ireland Corporation Tax rates guide for trading income, non-trading income, startup relief, R&D and large-group rules.
First Corporation Tax return and CT1 deadline
The CT1 is the company’s Corporation Tax return. A company generally files it and pays any balance nine months after the end of its accounting period. Electronic filing is normally due by the 23rd day of the ninth month.
The first period can be confusing because the incorporation date, trading start date, accounting period, preliminary tax date and first annual return date are not necessarily the same. Put every date in the calendar as soon as the company starts, and confirm the dates through Revenue or the company’s tax adviser.
A company may also have additional reporting duties, including Form 46G for certain payments to third parties. Keep an accurate supplier and contractor ledger so the filing can be assessed properly.
Preliminary tax: do not rely on a generic deadline
Preliminary tax is paid before the final Corporation Tax return and is credited against the eventual liability. The rules and options depend on factors including the company’s size, previous Corporation Tax liability and accounting period.
New-company timing is particularly easy to get wrong. Ask the company’s adviser to confirm whether the business qualifies as a small company for the relevant period and which payment option is available. The Revenue tax calendar should be checked for current deadlines.
Non-resident founders and Irish Corporation Tax
A founder does not need to live in Ireland to own or direct an Irish company, but non-resident formation can involve additional identity, director, address and bond requirements. Tax residence is a separate question from nationality and incorporation.
If the directors live abroad, review where the company is managed, where decisions are made, where work is performed, whether a treaty applies and whether the home country taxes the company or its owners. An Irish registration should never be marketed as a guarantee of zero tax outside Ireland or a guaranteed 12.5% result.
Start with our Irish company for non-residents guide and company tax registration checklist.
Common Corporation Tax registration mistakes
- Assuming CRO incorporation automatically completes Revenue registration.
- Using the wrong form or an outdated version of TR2.
- Registering with an unclear business activity description.
- Forgetting the Statement of Particulars after trading begins.
- Confusing the Corporation Tax deadline with the first annual return date.
- Assuming all company income is trading income at 12.5%.
- Leaving ROS access until the first filing is due.
- Failing to review VAT, PAYE/PRSI or RCT when the business expands.
- Promising a non-resident founder a tax result without residence and treaty advice.
First-year Corporation Tax checklist
- Save the CRO certificate, company number and constitution.
- Record the real trading start date and first taxable transaction.
- Register for Corporation Tax using the current Revenue process.
- Submit or confirm the Statement of Particulars within 30 days after trading begins.
- Set the accounting period and keep a monthly bookkeeping routine.
- Separate trading, passive, VAT and personal transactions in the records.
- Confirm preliminary tax timing with an accountant or tax agent.
- Prepare the CT1 and pay the balance by the correct ninth-month deadline.
- Review the first annual return, RBO and company-record deadlines separately.
Official sources and next steps
Check Revenue’s current tax registration guidance, Corporation Tax payment and filing guidance and basis of charge. Revenue guidance is the source to use for current forms and deadlines.
When you are ready to incorporate, start the Irish company formation process or review tax registration support. We can help you understand the formation route before you move on to accounting and tax compliance.