IW v SSWP & Anor (CSM)

For a child-support calculation under the 2012 scheme, historic income must be calculated using the figure last requested from HMRC. A tribunal cannot substitute non-HMRC evidence as the historic-income figure.

Current income, however, may be obtained from any source which the decision-maker or tribunal considers reliable. Where it exceeds the HMRC historic-income figure by more than 25%, it may instead form the basis of the calculation. A failure to identify the correct route is not material if the tribunal was entitled to reach the same result by using reliable current-income evidence.

The mother appealed to the First-tier Tribunal against a child-support assessment fixing the father's liability for three qualifying children at £128.98 per week. The First-tier Tribunal allowed her appeal and directed a recalculation from the same effective date using a higher gross weekly income supported by information she had produced.

The father appealed. The issue was whether the tribunal could use information supplied by the mother rather than HMRC, and whether the father's current-income information could support the higher calculation under the 25% rule.

1. Appeal dismissed. The First-tier Tribunal's decision involved no material error of law and stood.

2. Under regulations 35 and 36 of the Child Support Maintenance Calculation Regulations 2012, historic income is determined from the HMRC figure last requested by the Secretary of State. The statutory scheme therefore requires HMRC-sourced information for that purpose; evidence supplied by the mother could not itself replace the HMRC historic-income figure.

3. The position differs for current income. The regulations do not limit its source to HMRC. The decision-maker, and a First-tier Tribunal remaking the calculation, may use information from any reliable source. Thus, if the mother's evidence of the father's current income was reliable and showed an increase exceeding 25% over historic income, the tribunal could use it for the calculation.

4. The tribunal could also have sought the appropriate tax-year figures from HMRC. In deciding whether to seek such information, the welfare of affected children must be considered under section 2 of the Child Support Act 1991. Where reliable current-income information is unavailable, that welfare will ordinarily favour calculation using appropriately up-to-date figures.

5. Even if the First-tier Tribunal had wrongly treated the mother's evidence as historic-income evidence, the error made no practical difference. The same evidence could lawfully have been used as reliable current-income evidence, because the increase over the HMRC historic figure exceeded 25%.

• Upper Tribunal (Administrative Appeals Chamber): dismissed the father's appeal and upheld the First-tier Tribunal's decision.
• First-tier Tribunal, Birmingham: on 19 August 2014, allowed the mother's appeal against the agency's assessment and directed recalculation using a higher gross weekly income from the same effective date.