File your patent before your product is finished

File a patent when you can clearly explain the core mechanism, before you show it to outside investors or customers without an NDA, and ideally before due diligence on a funding round begins, not when the product feels "finished." Deep tech VCs typically check for a portfolio of patentable ideas, at least one active filing, and a founder who can defend it under direct questioning.

Most founders ask when to file a patent the wrong way. They treat it as a legal question (“is my invention finished enough?"), when investors treat it as a fundraising question (“does this team have a defensible business, or just a good idea?")

That distinction came up on a Lightbringer webinar, where our CCO Ola Wassvik sat down with Tommy Myrvang, founder of Cler, a Swedish deep tech company replacing air filters with a self-cleaning, filter-free system. Tommy walked through exactly how his IP strategy became the thing that tipped a VC from maybe to yes, including the moment a patent lawyer stress-tested his invention live, in front of the investment committee, and said "my god, that is clever."

Watch the full conversation: Patent Strategy & Fundraising Tips for Deep Tech Startups, the complete story, in Tommy's own words.

The rest of this piece isn't a recap. It's the decision framework that the story points to: a practical answer to when you should file, whatever stage you're at.

Why patent timing matters more when you're raising money

For a software startup, a strong founding team can be enough to unlock a check. For hardware and deep tech, that shortcut doesn't exist. Investors need to see something real before they'll dig into whether you actually own it.

That's the core of a startup patent strategy for deep tech: whether you're patenting your idea as a startup founder for the first time or building out a portfolio, filing isn't about racing to protect an idea the day you have it. It's about filing at the point where it changes how an investor reads your business, from "interesting technology" to "defensible technology, run by a team that knows what it's protecting."

Why "not ready yet" isn't a reason to wait

Deep tech founders often delay both fundraising and patent filing because the product feels unfinished. That instinct gets the causality backwards. A stripped-down, imperfect version of your technology, tested honestly with real customers, is usually what earns investor attention, precisely because it proves the mechanism works outside a lab or a deck.

The lesson for protecting your invention while you're still building it: you don't need a finished product to have something worth filing on. You need a core mechanism that works, that you can explain clearly, and that you're not afraid to test in the real world before it's polished.

What changes once a VC is involved

Grant funding rarely asks hard follow-up questions about IP. VCs do, and they typically bring in an outside patent expert to ask them directly, sometimes in front of the whole investment committee. That's the difference between IP for fundraising and IP as a formality: a portfolio of patentable ideas and at least one active filing reads as follow-through, not just strategy on paper. (For the full checklist of what that due diligence process actually covers, see our guide to IP due diligence for investors.)

The practical takeaway: get to the point where you, not just your patent attorney, can defend the invention under direct questioning, before that conversation happens, not during it.

A practical framework for when to file

Instead of asking "is my invention finished," ask these four questions:

1. Can you describe the core mechanism clearly, in plain language? If a patent lawyer (or an investor's advisor) can't follow the explanation, it's not ready to file, but it also means you can't yet defend it in due diligence either.
2. Does it solve the problem in a way a competitor couldn't trivially copy once they see your product? That's usually the signal that you have something worth protecting, even if the surrounding product isn't finished.
3. Are you about to show the technology to outsiders, customers, pilot partners, or investors, without an NDA? That's a hard deadline, not a soft one. Public disclosure before filing can cost you the ability to patent at all in many jurisdictions.
4. Is a funding round on the horizon? If IP due diligence is coming in the next 6–12 months, filing before that conversation starts, even a single, well-chosen provisional application, gives you something concrete to point to instead of a promise to file later.

If two or more of these are true, you're not too early. You're at the point most deep tech founders wish they'd filed sooner.

Owning your timeline with investors

Founders who navigate this well tend to share one habit: they don't oversell where the technology is. They break their roadmap into concrete, sub-deliverable milestones, so investors can see exactly what's done, what isn't, and when the rest will land, including being upfront when full commercial maturity is still years out.

That honesty should extend to IP. Present a patent not as "protection for a finished product," but as part of an evolving strategy, a first filing, backed by a pipeline of further ideas, with everyone aligned on what comes next. Investors doing this kind of diligence aren't looking for a startup with zero open questions. They're looking for a founder who already knows the answers, or knows exactly how they'll get there.

If you want the broader playbook for building that kind of roadmap beyond a single filing, our guide on patent strategy for growing tech companies covers how to structure a portfolio by funding stage, and our piece on how patents influence funding, valuation, and exit potential breaks down the connection between IP and your cap table conversations.

FAQ

Do I need a patent before raising VC money?
Not always, but you need a real answer when it comes up. If you're targeting deep tech or hardware-focused VCs, expect the question to surface during due diligence, and treat "we have a filing and a pipeline of further ideas" as the answer that lands best.

Can I patent an idea for free before I have full funding?
it isn't free with us but we endeavour to get you the best protection which is worth investing in. What you can do is start with a provisional application, which buys you 12 months to develop the invention further before deciding whether to move forward with the complete application. At Lightbringer, both are flat fee, so you know the exact cost before you commit either way, no hourly billing and no invoice shock.

What happens if I show my product to investors before filing?
In the US, public disclosure, including an unprotected investor demo, starts a 12-month grace period on your own disclosure, under the America Invents Act's first-inventor-to-file rules; most other countries offer no grace period at all, so an early demo can eliminate patentability outside the US entirely. Get an NDA in place, or file first if the disclosure is unavoidable.

How do I know if my invention is ready to patent?
If you can explain the core mechanism clearly enough that a patent attorney could ask you specific follow-up questions and get concrete answers, it's ready, even if the surrounding product isn't finished.

Wondering whether your invention is ready to file, or how to explain your IP strategy to investors? Get your first patent with a free consultation with a Lightbringer patent attorney and find out where you actually stand.

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