Comparison
Two fixed-fee, no-subscription routes. FounderCatalyst papers your whole raise; Seisly prepares advance assurance on its own. Here is an honest comparison of when each is the better buy.
| Seisly ✦ | FounderCatalyst | Hiring a lawyer | |
|---|---|---|---|
| Headline price | £75 flat (advance assurance only) | £1,495 + VAT fixed (full raise, AA included) | ~£1,000–£10,000 |
| What you get | Advance assurance prepared, plus optional filing | Round legals + AA + compliance + cap table + options | Bespoke |
| Buy advance assurance on its own? | Yes – £75 | No – bundled in the £1,495 package | Yes, quoted |
| Subscription required | None | None | None |
| Scaling fees | None | None | Sometimes |
| Best suited to | Founders who only need advance assurance now | Founders papering a whole raise in one fixed fee | Complex / bespoke structures |
Scroll across to compare all three →
Prices verified against seisly.com and foundercatalyst.com, June 2026. Lawyer fees are a typical market range.
Seisly charges a flat £75 for the advance assurance application, with HMRC filing as an optional add-on. FounderCatalyst charges £1,495 + VAT, fixed, for its complete service: your round's legal paperwork, cap table, option schemes and SEIS/EIS advance assurance bundled together, with advance assurance included at no extra cost. The two are not quite like-for-like: FounderCatalyst papers the whole raise; Seisly focuses on the one application.
If you need the entire raise documented – investment agreement, articles, advance assurance and compliance, cap table, EMI and unapproved options – FounderCatalyst does all of it for one fixed £1,495 with no subscription and advance assurance included. For a founder ready to run a full round, that is genuinely strong value.
If, right now, you only need advance assurance – to test investor appetite, because you are very early, or because you are handling the round itself elsewhere – Seisly prepares it for £75 rather than £1,495 for a full package you do not yet need. Done for you, with optional HMRC filing.
Genuinely complex or bespoke structures, or formal advice an investor requires.
For advance assurance on its own, yes – £75 against FounderCatalyst's £1,495 fixed fee. But they are not like-for-like: FounderCatalyst's fee papers your whole round with advance assurance included, while Seisly does the advance assurance application alone. Full raise: FounderCatalyst is strong value. Advance assurance only: Seisly is the cheaper, narrower route.
FounderCatalyst is a fixed-fee platform for your entire raise – round legals, cap table, options and advance assurance bundled into one £1,495 package. Seisly does one step: prepare, and optionally file, your advance assurance application for £75. Different scope; both honestly fixed-price.
Their advance assurance is included within the £1,495 complete service rather than sold on its own. If advance assurance is genuinely all you need right now, Seisly prepares it separately for £75.
FounderCatalyst – that is what it is built for. Seisly is the specialist for the advance assurance step, not the whole round.
Seisly drafts from a short questionnaire, usually under an hour. HMRC then typically takes 4 to 8 weeks, whichever route you use.
Figures verified against foundercatalyst.com/pricing; foundercatalyst.com/seedlegals-alternative; seisly.com, June 2026. Competitor prices and HMRC thresholds are taken from primary sources, not from either party's marketing about the other.
Check whether you qualify in about five minutes, free. If your case needs more than an application, your report will tell you.
From £75. No account, no email sign-up.