About Seisly

If you have read this far, you have everything you need to get started.

Seisly is an AI-powered platform for SEIS and EIS advance assurance applications. Founders prepare their application through the platform, an AI layer assembles the supporting structure and reviews it against the specifications set out in this Playbook, and a human review pass happens before anything goes to HMRC.

The platform exists because the existing market sits at two extremes. On one side, founders self-submit with no preparation, get caught by the language issues Sections II and III cover, and waste months on refusals. On the other, professional firms charge several thousand pounds for what is essentially a structured document-drafting exercise. Seisly's tiered structure occupies the missing middle – and because the preparation and diagnostic are already done, a firm on the Seisly Advisers panel can review and sign off a clean application for £500–£1,000 rather than the cost of building it from scratch. The founder chooses the level of professional involvement that matches their case, instead of paying for a service the case doesn't need.

For cases that need professional sign-off, Seisly Advisers is a small panel of vetted UK firms specialising in SEIS and EIS work. The same Seisly-generated draft is the starting point; the firm reviews, refines, and signs off on its own letterhead. For complex cases beyond the reach of the standard process, the panel is also where founders are introduced to specialists.

Sanjay Wadhwani. Founder of Seisly. SEIS and EIS practitioner since 2012, when he founded the UK's first SEIS-dedicated fund within months of the scheme's launch. The Playbook is built on the patterns observed across the SEIS applications, fund investments, and adviser conversations of the years since.

Background and contact details at linkedin.com/in/sanjaywadhwani.

An advance assurance letter from HMRC is a statement that, on the facts presented, the company appears to meet the SEIS or EIS conditions. It is not a binding guarantee. The actual relief is granted later, at compliance statement stage, after the shares have been issued and the company submits an SEIS1 or EIS1. HMRC can take a different view at that point if the facts have drifted from what was set out in the application, if the use of proceeds has changed, if the share rights have shifted, or if the trade has moved in a direction that crosses an excluded line. A clean advance assurance is the strongest possible starting position. It is not the end of the analysis.

Disclaimer. This Playbook is for general guidance only and does not constitute professional tax, legal, or financial advice. SEIS and EIS rules are set by HMRC and may change; this Playbook reflects the position as at February 2026. Where the Playbook's working summaries differ from HMRC's published guidance or the underlying legislation, HMRC's guidance and the legislation take precedence. Readers should obtain professional advice on their specific circumstances before submitting an advance assurance application.