Taxes Consolidation Act 1997 section 1090

Income tax assessment to be conclusive of total income

Section 1090 provides that once an income tax assessment becomes final and conclusive, it is binding for all income tax purposes and cannot be reopened on grounds of reduced income or loss unless prior relief claims were made.

• A final and conclusive income tax assessment is also final for estimating total income from all sources under the Income Tax Acts.
• The assessed income figure cannot be revised downward after the assessment becomes final, even if actual income was lower or a loss arose.
• No allowance or adjustment for diminished income or losses may be taken into account unless a claim was previously made under the relevant statutory provisions.
• Loss relief claims must be made under the specific provisions of the Income Tax Acts (principally Part 12) before the assessment becomes final.