Not in this estimator. A valid SEIS Income Tax carry-back election may permit a cross-year claim, but the year matching and claim must be checked separately.
Seis Reinvestment Relief Calculator UK
Enter your values below to get the result first, then scroll for the full explanation and guidance.
SEIS exempt gain not calculated
Review claim conditionsSame-year eligible claim only
SEIS exempt gain not calculated: Review claim conditions (Same-year eligible claim only)
This estimate requires a confirmed 2026/27 gain, 2026/27 SEIS shares and Income Tax relief actually obtained on those shares.
What to watch
This estimate requires a confirmed 2026/27 gain, 2026/27 SEIS shares and Income Tax relief actually obtained on those shares.
Result snapshot
A quick visual read of the values behind this result.
This calculator updates instantly as your values change, so you can compare outcomes without extra steps.
Carry-back, cross-year matching, withdrawn relief and final CGT liability are outside this estimate.
Try different values to compare results.
Estimate the part of a 2026/27 chargeable gain that may be exempt when qualifying SEIS expenditure is matched to that gain and SEIS Income Tax relief was obtained.
SEIS exempt gain not calculated
Review claim conditionsSame-year eligible claim only
SEIS exempt gain not calculated: Review claim conditions (Same-year eligible claim only)
This estimate requires a confirmed 2026/27 gain, 2026/27 SEIS shares and Income Tax relief actually obtained on those shares.
What to watch
This estimate requires a confirmed 2026/27 gain, 2026/27 SEIS shares and Income Tax relief actually obtained on those shares.
Result snapshot
A quick visual read of the values behind this result.
This calculator updates instantly as your values change, so you can compare outcomes without extra steps.
Carry-back, cross-year matching, withdrawn relief and final CGT liability are outside this estimate.
Try different values to compare results.
Table of Contents
Table of Contents
About Seis Reinvestment Relief Calculator UK
Seis Reinvestment Relief Calculator UK helps you work through the main numbers for this topic quickly with a simple input flow and an instant result.
Use the calculator result as a practical starting point, then review the explanation and assumptions on the page if you want more context.
Matching the SEIS gain and investment
For post-2012/13 gains, 50% of the qualifying amount matched to an unmatched gain can be exempt. The amount is restricted by unused investment expenditure, the SEIS investor limit and the share amount on which Income Tax relief was obtained. It is not an estimate of CGT saved.
Formula explained
Calculation flow
This calculator is structured for fast UK-focused estimates with clear inputs, repeatable logic, and instant results.
Formula
Input values -> calculation engine -> instant result
How the result is built
1Enter the values requested in the form.
2The calculator applies the configured formula logic.
3The result updates instantly with a breakdown.
4Use the output to compare scenarios quickly.
Example
Enter an unmatched gain, allocated SEIS expenditure and relief actually obtained.
Assumptions
- Same-year 2026/27 eligible claim only. Excludes carry-back, cross-year matching, withdrawn relief and CGT liability calculations.
Source basis
- UK-focused calculator flow
- Structured input validation
- Instant result breakdowns
FAQ
Common questions
Trust and notes
Assumptions and important notes
This calculator is designed to give a fast estimate using the method shown on the page. Results are most useful when your inputs are accurate and the tool matches your situation.
Use the result as guidance rather than a final diagnosis or professional decision. If the result could affect health, legal, financial, or compliance decisions, verify it with a qualified source where appropriate.
- Same-year 2026/27 eligible claim only. Excludes carry-back, cross-year matching, withdrawn relief and CGT liability calculations.
Method
UK calculator guidance
Last reviewed
April 17, 2026