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  • Product: ONESOURCE Corporate Tax

IE - August 2026

ONESOURCE Corporate Tax v18.0

Release summary

For documentation and other product information, search the Customer Center.
This release is primarily to provide the new packs supporting computation and group templates for periods ending in 2026, although updated packs for periods ending in 2025 are also included.
We have included a number of legislative and schema updates, details of which are included in the notes that follow:
  • R&D credit updates in respect of claims made under section 766C and/or section 766D.
  • Support for balancing allowances on specified intangible assets under section 291A.
  • Support for the enhanced deduction under section 81E.
  • Support for the rental income exemption under section 222A (cost rental dwellings).
  • Support for the living city initiative (living over the shop) under section 372AAE.
  • Support for the unscripted production corporation tax credit under section 487A.
Unless otherwise stated, all changes detailed are available for 2026 files only.

Form CT1 update

Area of change
Details and limitations
New CT1 forms
We have updated ONESOURCE to include the latest version of the Corporate Tax return (Form CT1) and associated e-filing rules and validations for 2025 and 2026. An error message will appear on existing unsubmitted 2025 files prompting you to erase and re-develop the return forms.
There are a number of changes in the 2026 return, requiring changes to other computation sheets. These changes are described below.
important
  • We are discovering, and being made aware of, an increasing number of e-filing issues on ROS's side, particularly relating to validations in the RPF. We report all issues to ROS, and we will continue to monitor these issues for resolution.
  • Please contact the ONESOURCE Support Team if you have any concerns or need any assistance.
Research & Development – claims under Sec. 766C and Sec. 766D
The following changes have been made to the 'new rules' R&D sheets:
Research and Development Expenditure Credit Summary Sec. 766C
  • A new Tax Credit at 35% row has been added for accounting periods ending on or after 21 December 2026 (i.e. accounting periods with a specified return date on or after 23 September 2027).
  • For accounting periods ending on or after 21 December 2026, the de minimis for the first instalment is increased from €75,000 to €87,500.
Research And Development Credit Surrender - Employee Details Sec. 766C
  • The PPSN and Amount fields relating to credit surrendered to key employees have been updated so that multiple entries can now be made on the Form CT1. Previously, only one entry could be recorded for these fields.
Research and Development Capital Credit Sec. 766D
  • A new Credit at 35% available in current period row has been added for qualifying accounting periods.
S291A balancing allowances
To assist with the completion of the new disclosures in the Form CT1 relating to balancing allowances and capital expenditure on specified intangible assets, the
Adjustment of Profit
 sheet has been updated.
New
IP BA Depreciation Memo
 and
IP BA Fixed Allowances Memo
 sections have been added to the
Adjustment Of Profit
 sheet, along with new rows to the
IP Results Memo
.
The existing
IP CA Depreciation Memo
 and
IP CA Fixed Allowances Memo
 have been updated to now show capital allowances only, with balancing allowances separately identified in the new
IP BA Depreciation Memo
 and
IP BA Fixed Allowances Memo
 sections.
S81D stock exchange listing expenditure
To assist with the completion of the new disclosure in the Form CT1 for deductions claimed in respect of stock exchange listing expenditure under Sec. 81D, a new row has been added to the
Adjustment Of Profit
 sheet for stock exchange listing expenditure claimed under Sec. 81D.
The stock exchange listing expenditure disclosure on the
Extract of Accounts
 sheet will only be displayed where applicable for accounting periods ending in 2025.
S81E enhanced deduction
To assist with the completion of claims under Sec. 81E, a new
Sec. 81E Expenses
 sheet is developable from the
Profit and Loss Account
.
The sheet enables the analysis of expenditure eligible for the enhanced deduction and calculates the additional deduction available under Sec. 81E.
A new row, enhanced deduction under Sec. 81E, has been added to the
Adjustment Of Profit
 sheet to reflect the enhanced deduction claimed.
The
Sec. 81E Expenses
 sheet also includes the information required to support the corresponding Form CT1 disclosures, including:
  • Enhanced deduction claimed under Sec. 81E.
  • Eligible expenditure incurred in respect of completed developments.
  • Number of apartments in the completed developments.
  • Confirmation where the company is a relevant contractor for the purposes of Sec. 81E.
A validation has also been added to ensure that the enhanced deduction claimed does not exceed the legislative limit based on the number of apartments entered.
Rental income exemption (S222A)
To assist with the completion of the new rental income exemption under Sec. 222A disclosures in the Form CT1, a new
Cost Rental Analysis
 sheet is developable from the
Rental Income
 and
Property Summary
 sheets.
A new qualifying cost rental dwellings summary table has been added to the
Property Summary
 sheet to summarise qualifying cost rental dwelling income and related disclosures.
A new row has been added to the
Property Summary
 sheet for the confirmation that the conditions for the exemption have been satisfied.
The
Rental Income
 sheet has been updated to include a new qualifying cost rental dwellings total column to separately identify qualifying income eligible for exemption under Sec. 222A.
Additional validations have been added to ensure that the required information is completed where qualifying cost rental dwelling disclosures are required.
S372AAE living over the shop
To assist with the completion of the new sections in the Form CT1 for Sec. 372AAE Living City Initiative (living over the shop), a new option has been added to the Incentive Scheme Type dropdown on the
Industrial buildings allowance
 sheet.
A new row has been added to the
Living City Initiative and Aviation Services Facilities
 and
IBA Incentive Schemes Summary
 sheets.
Residency details
The Residency Details section on the
Information For The Return
 sheet has been updated to include the following new fields:
  • Tax Identification Number for the country of residence.
  • Company name in that country.
  • Address in that country.
Where the company is trading through a branch or agency, these new fields, together with the existing fields, are now mandatory to ensure the required information is provided for e-filing.
De minimis aid
To assist with the completion of the new sections in the Form CT1 for Sec. 372AAE Living City Initiative (Living over the Shop), a new row has been added to the
De Minimis Aid
 sheet.
Transfer pricing
The wording of the following questions has been updated on the
Information For The Return
 sheet:
  • Is the company required to prepare a Local File under section 835G?
  • Is the company required to prepare a Master File under section 835G?
A validation has also been added to identify inconsistent responses where
Is the company part of a multinational group?
 is answered No, but
Is the company part of a multinational group which is required, whether in Ireland or elsewhere, to file a country-by-country report?
 is answered Yes.
Leasing losses
To assist with the completion of the corresponding disclosures in the Form CT1, a new Clause V column has been added to the
Leasing losses surrendered details
 and
Leasing losses claimed details
 sheets.
Digital games relief
Wording on the
Digital Games Corporation Tax Credit
 sheet has been updated to match the RPF.
The following fields have been removed:
  • Accounting period in which expenditure incurred begin date
  • Accounting period in which expenditure incurred end date
Unscripted production corporation tax credit
To assist with the completion of claims under Sec. 487A, a new
Unscripted Production Corporation Tax Credit
 sheet is developable from the
Corporation Tax Computation
 sheet.
The sheet supports the completion of both Unscripted Production Corporation Tax Credit claims under Sec. 487A(21) and Unscripted Production Corporation Tax Credit claims under Sec. 487A(22) for the Form CT1.
A new row has been added to the
Corporation Tax Computation
 sheet to incorporate the credit, any refundable amount arising, and any clawback amount taxable under Schedule D Case IV.
A new row has been added to the
Self Assessment Made Under Chapter 4 Of Part 41A
 sheet to deduct the tax credit from the amount of tax chargeable for this period.
Slurry storage
The following fields have been removed from the Form CT1:
  • If any amount of Machinery and Plant allowance claimed above in (a) is in respect of slurry storage (section 658A(2)(b)) enter the amount here.
  • If any amount of Farm Buildings Allowance claimed above is in respect of slurry storage (section 658A(2)(b)) enter the amount here.
The Slurry storage – Sec. 658A(2)(b) option has been removed from the
Plant and Machinery
 sheet and
Industrial Buildings Allowance
 sheet for accounting periods where these disclosures are no longer required.
Sec. 299 Leases
The wording on the
Sec. 299 Leases agreed with Corporate Lessors
,
Sec. 299 Leases agreed with Corporate Lessees
 and
Sec. 299 Leases agreed with Individual Lessees
 sheets has been updated to reflect revised legislative references.
The following fields have been removed from the Form CT1:
Sec. 299 Leases agreed with Corporate Lessees
  • Total claimed under S299(5)(h)(ii) in respect of a relevant lease or leases.
Sec. 299 Leases agreed with Corporate Lessors
  • Total claimed under S299(6)(b)(ii) in respect of a relevant lease or leases.

Other changes

Area of change
Details and limitations
Interest limitation
The Single Company Worldwide Group (SCWG) question has been updated to align with the latest Form CT1 requirements.
The available responses for the SCWG question are now dependent on the responses provided for membership of an interest group and the de minimis exemption:
  • Where the company is a member of an interest group, the SCWG question is not applicable.
  • Where the company is not a member of an interest group and the de minimis exemption does not apply, the SCWG question must be completed with either Yes or No.
  • Where the company is not a member of an interest group and the de minimis exemption applies, the SCWG question may be completed with Yes, No or N/A.
These changes have been made to the
Interest Limitation and Detailed Interest Limitation
 sheets.
These changes have also been made in new and existing 2025 files.
Section 291A(4) TCA 1997 election
The logic for the question
Are you making an election under Section 291A(4) TCA 1997?
 on the
Information For The Return
 sheet has been updated to align with the treatment of specified intangible asset additions.
The election will now automatically be marked as Yes where there is at least one specified intangible asset addition in the accounting period and fixed allowances at 7% are being claimed in respect of those assets.
Where there is at least one specified intangible asset addition in the accounting period, but no specified intangible asset allowances are being claimed, a new clearable validation has been added to prompt the user to review whether a Sec. 291A(4) and/or Sec. 291A(10) election is required on the
Plant and Machinery
 sheet. Clearing the validation adds to the audit trail.
These changes ensure that the Sec. 291A election is completed where required and highlight potential omissions for review prior to e-filing.
These changes have also been made in new and existing 2025 files.
Research & Development – Other changes
Research and Development Expenditure Credit Sec. 766C
  • The validation requiring group relief claimed or surrendered amounts to be entered in multiples of four has been removed from the
    Research & Development Credit Under Sec. 766C
     sheet following updates to the Revenue Online Service (ROS) e-filing validations.
This change has also been made in new and existing 2025 files.
Digital games relief
New rows have been added to the
Self Assessment Made Under Chapter 4 Of Part 41A
 sheet for:
  • To deduct the digital games credit from the amount of tax chargeable.
  • Digital games credit.
  • Digital games offset.
The digital games credit has also been incorporated into the Reconciliation to Self-assessment section on the
Corporation Tax Computation
 sheet.
These changes have also been made in new and existing 2025 files.
Other changes
In additional to the changes described above, the following error corrections and enhancements have been made:
  • Where a qualifying financing company loan relates to only one period of a long period of account, the disclosure will now be included only in the relevant period's submission.
  • The date displayed in the Non-resident Landlord Withholding Tax section has been updated to 2023 to align with the Form CT1.
  • Corrected the validation on the
    Outbound Payments
     sheet for the second period of a long period of account to reference the correct period checkbox on the
    Information For The Return
     sheet.
These changes have also been made in new and existing 2025 files.

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