SEIS Carry Back: Claiming Relief for a Previous Year
How the carry back election works, when it pays, and the mechanics of claiming SEIS relief against last year instead of this one.
In this article
SEIS carry back is the rule that lets you move relief through time. Any part of a subscription can be treated as if made in the previous tax year and claimed against that year’s bill instead. SEIS carry back exists because income is lumpy and investments are not polite about timing, and used deliberately it is the difference between relief on paper and relief in your bank account.
How the SEIS carry back election works
You choose an amount, all of the subscription or any slice, and elect on your claim to treat it as invested in the prior tax year. The elected slice then plays by that year’s rules: it must fit within the £200,000 annual limit alongside anything you actually subscribed then, and the relief is capped by that year’s tax bill. There is no separate form; the election rides on the SEIS3-based claim itself, as shown in the claiming guide.
The three situations where it pays
- Last year was bigger. A bonus year, a business sale, a final salary before stepping back: carry the relief to where the tax was.
- You want the cash sooner. A carried-back claim against a filed year generates a repayment of tax already paid, rather than waiting to offset a future bill.
- This year cannot absorb it. Relief cannot exceed the bill; if this year’s tax is thin, the balance is wasted unless it travels back.
Worked example
You invest £60,000 in June 2026. This year you expect £9,000 of income tax; last year you paid £41,000. Claim £18,000 of the subscription this year (using £9,000 of relief) and carry back £42,000 (£21,000 of relief) to last year. Total relief: £30,000, the full 50%, where a same-year-only claim would have stranded £21,000 of it. The split is yours to choose; the arithmetic rewards ten minutes of planning.
The limits that police it
- One year back only. SEIS carry back reaches the previous tax year, no further.
- The receiving year’s £200,000 cap counts your actual subscriptions that year plus everything carried into it.
- The receiving year’s bill is still the ceiling; carry back moves relief, it does not mint it.
- Reinvestment relief does not travel: the CGT exemption in the CGT guide matches gain and subscription in the same year; carrying the income tax relief back does not drag the gain with it.
Mechanics and deadlines
Claim through Self Assessment using the SEIS3, electing the carried amount, or amend the earlier return once the certificate arrives. The five-year claim window, running from 31 January after the tax year of the actual investment, covers carried-back claims too. Fund investors note: deployment timing decides which year each certificate belongs to, which is where carry back earns its keep untangling fund timetables.
When not to use SEIS carry back
The election is optional, and sometimes rightly declined. If last year’s bill was smaller than this year’s, the relief belongs where you are. If last year already carries SEIS subscriptions near the £200,000 ceiling, the carried slice may not fit. And if the earlier return has complexities you would rather not reopen, an amendment purely for carry back deserves a cost-benefit thought. The election exists to serve the arithmetic, not to be used reflexively; run both years’ numbers, or hand the pair to an accountant, before ticking the box.
Common questions
How does SEIS carry back work?
You elect to treat some or all of a subscription as made in the previous tax year and claim the 50% relief against that year’s bill, within that year’s £200,000 limit.
How far back can SEIS relief be carried?
One tax year only.
Can I split an investment between two years?
Yes, in any proportion, provided each year’s limit and tax bill can absorb its share.
Does carry back also move reinvestment relief?
No. The CGT reinvestment exemption requires the gain and subscription in the same tax year regardless of the income tax election.
