How to Claim SEIS Tax Relief (Step by Step)

How to claim SEIS tax relief is, at heart, a paperwork exercise with one non-negotiable ingredient: the SEIS3 certificate the company gives you after HMRC has processed its compliance statement. With the SEIS3 in hand, you claim through your Self Assessment return, or in-year through your PAYE code, and you have up to five years to do it. Step by step:

First, understand the timeline

You cannot claim on day one. The company must trade for at least 4 months and spend at least 70% of the money raised, then file form SEIS1 with HMRC. HMRC authorises it (form SEIS2) and only then can the company send you the SEIS3. In practice, months pass between investing and claiming, which surprises first-time investors and is nobody’s fault.

How to claim SEIS tax relief, step by step

• Step 1: receive your SEIS3. Chase the company politely if it is slow; no certificate, no claim. Check your name, the amount and the unique investment reference.
• Step 2: choose your year. Claim in the tax year of the investment, or carry all or part back to the previous year, whichever uses the relief best.
• Step 3: claim on your return. In the Additional Information pages of Self Assessment, enter the total SEIS subscriptions and the details from your SEIS3. If you do not normally file a return, you can claim on the form inside the SEIS3 itself.
• Step 4 (optional): claim in-year through PAYE. Employed and impatient? Send the SEIS3 claim form to HMRC and they can adjust your tax code rather than waiting for year-end.
• Step 5: claim the CGT reliefs where relevant. Reinvestment relief is claimed on the same form and pages; disposal relief needs no claim, it simply applies after three years if conditions held.

The deadline

Five years from the 31 January following the tax year in which you invested. Generous, but not infinite, and late paperwork is the most avoidable way to lose money this scheme offers.

Keep the records

The SEIS3 itself, your subscription documents, and a note of dates and amounts. You will want them again if you claim loss relief later, and the three-year conditions in the reliefs guide all hang off these papers.

Carry back, with the arithmetic shown

Carry back treats some or all of this year’s subscription as if made last year. Suppose you invest £40,000 in 2026 to 2027, but last year your income, and therefore your tax bill, was far higher. Electing to carry the full £40,000 back claims the £20,000 relief against the earlier year, generating a repayment of tax you have already paid, often the fastest cash the scheme ever produces. The limits belong to the receiving year: the carried-back amount must fit within that year’s £200,000 cap alongside anything you subscribed then. You make the election on the claim itself, and you can split an investment between the two years in any proportion that fits.

The PAYE route in detail

Employees who do not want to wait for a tax return can send the claim form from pages 3 and 4 of the SEIS3 to HMRC and ask for the current year’s relief through their tax code. HMRC adjusts the code, your monthly deductions fall, and the relief arrives as improved take-home pay across the remaining months. Two caveats: code-based relief is provisional until reconciled, and anything complicated, carry back, reinvestment relief, multiple certificates, belongs in a return rather than a coding notice.

Claiming the CGT reliefs

Reinvestment relief rides on the same claim: the SEIS3 form and the Self Assessment capital gains pages between them identify the gain, the SEIS subscription and the 50% you are exempting, in the same tax year as the gain. Disposal relief, the exemption when you eventually sell at a profit, needs no claim at all; you simply return the disposal as exempt, provided the three-year conditions held. The interlocking rules live in the reliefs guide.

When the paperwork misbehaves

• SEIS3 late? Chase the company; the delay is usually HMRC processing or founder admin. Your five-year window is generous, but do not let a certificate die in someone’s drawer.
• SEIS3 wrong? Name, amount or reference errors go back to the company for reissue. Do not claim on incorrect paper.
• Return already filed? Amend it within the amendment window, or make an overpayment relief claim inside the five years.
• Certificate lost? The company can provide a replacement; HMRC’s reference number does the heavy lifting.

Handing it to your accountant

If someone files for you, hand them a one-page pack per investment: the SEIS3, the subscription date and amount, your carry-back preference, and any gain you are matching for reinvestment relief. Five minutes of assembly converts directly into a smaller bill and a faster repayment.

A complete claim, end to end

Put the pieces together. You subscribe £15,000 in October 2026. The company trades, spends and files; your SEIS3 arrives in July 2027 showing the unique investment reference. Last year’s income was higher, so you elect to carry the whole amount back to 2025 to 2026: you enter £15,000 and the reference in the Additional Information pages of the return you are filing anyway, HMRC reprocesses the earlier year, and £7,500 lands as a repayment. Total admin: one certificate checked, two boxes completed, one election ticked. The scheme’s paperwork reputation is worse than its paperwork.

Sources

HMRC HS393 · gov.uk, Apply to use SEIS