I built DeadlineSentry in a weekend for $12 - a free tool that tells you tour LLC's filing deadline and what missing it costs

You've put your finger on the actual pricing question, and I'll be honest that I can't answer it with data yet — no paid signups to read a pattern from. But here's how I think about it.
My hunch is that willingness to pay splits exactly along the line you drew: people who've already eaten a late fee convert on fear-memory ("$500 gone over a form I forgot"), and for them $12/mo isn't a purchase, it's cheap insurance against a specific pain they can still feel. First-timers who've never missed one are a much harder sell, because you're asking them to pay to prevent something they don't yet believe will happen to them. Prevention is always a weaker motivator than relief.
If that's right, it changes the SEO targeting, not just the pricing. There are two flavors of intent in these searches: preventive ("when is the florida llc annual report due") and already-burned ("florida llc reinstatement," "llc late fee," "my llc was administratively dissolved"). The burned queries are lower volume but they're the people who'll actually pay, and reinstatement guides are already on my build list partly for that reason. The preventive traffic is bigger and better for list-building; the burned traffic is smaller and better for revenue.
And the honest hedge: I don't have to resolve which theory is right before earning a dollar. If someone burned once wants tracking today, I can take payment on a Stripe link and run their reminders by hand long before the automated tier exists — so the "do people pay before or after getting burned?" question gets answered by real transactions instead of speculation. That's the next thing I'm actually watching for.
Good comment — the "burned vs not-yet-burned" frame is going in the operating doc.

Bit of both, but leaning toward "scratch my own itch, then let search validate it." The itch was real — LLC annual report deadlines are boring, easy to miss, and expensive to get wrong, so I already believed the pain existed. What I didn't do was survey people or collect a pre-launch waitlist. I shipped the checker and I'm using the market as the validation instrument instead of trying to predict it.
Early signal, and I want to be honest that it's early: no email signups yet. What I can see is that organic Google indexed the state queries within a couple of days and the traffic showing up is exactly the intent I'd want — people searching "[state] LLC annual report deadline" already know what they need. Reddit traffic, by contrast, bounced. So the read isn't "this is validated," it's "the right people are findable and arriving." Conversion is the next thing I have to earn, not something I can claim yet.
On your actual question — how much validation is enough — I don't think shipping and validating are really opposites. Shipping is validation, as long as you build the smallest thing that produces a real signal, and then actually instrument it. The trap isn't building too early, it's building too much before you've set up a way to learn the truth. So I'd flip the question from "have I validated enough to build?" to "what's the smallest thing I can ship that will tell me the truth?" — then ship that and watch the numbers instead of your hopes. I'm still in the watching phase.

This is exactly the kind of trap the product exists for, and you've described the deeper problem better than my landing page does: the worst obligations aren't the ones with scary deadlines, they're the ones you don't know apply to you. Form 5472 is the poster child — a paperwork filing with a $25,000 penalty, owed by people who often have no US accountant, filed with a pro-forma return that makes no intuitive sense, and silently out of scope for most formation services. The mismatch between "how invisible it is" and "what it costs" is almost comically cruel.
Honest answer to your question: not yet. v1 branches on state + entity type + formation date, and it only covers state-level filings — the federal layer (5472, BOI, etc.) isn't in there. But foreign-owned single-member LLCs are now explicitly on the roadmap, because the profile is perfect for this tool: highest stakes, least local knowledge, and the formation services that set these LLCs up are exactly the stale-email-on-file problem that makes reminders fail. A "who owns this LLC?" question added to the checker unlocks the whole branch.
One caveat I'll hold myself to: anything federal/tax-adjacent gets added carefully and clearly labeled, because a wrong answer about a $25K penalty is worse than no answer. Thanks for the flag — genuinely one of the most useful comments on this thread. Mind if I follow up when the foreign-owner branch ships?

That's exactly the plan, yeah — the paid tier is gated on signal, not on a build schedule. Right now the roadmap is basically: publish state guides (each one is a new search doorway), keep the checker's data verified, and watch visitor→email rate. The build trigger is a conversion threshold, not a date.
One nuance I'd add: "double down on SEO first" and "have a paid tier" turn out not to be sequential. If someone from the waitlist wants deadline tracking today, I can take payment with a Stripe link and run their reminders manually behind the scenes — concierge-style — long before the automated product exists. So SEO gets 90% of the effort, but demand never gets turned away while I build. The software gets written when doing it by hand stops scaling, which is the best possible reason to write software.
The 48-hour indexing surprised me too, for what it's worth. I expected months of sandbox. Long-tail state-specific queries seem to have shallow enough competition that a new domain can slot in fast — the harder climb will be the head terms.

This is a sharp catch, thank you. You're right that the current CTA leads with the mechanism (reminders at 90/60/30/7 days) when it should lead with the avoided loss. "Reminders" is a feature; "not paying $400" is the reason anyone cares. Shipping your version of the copy today — the loss-framing also matches how people arrive at the site in the first place, since most of them just read about the penalty two paragraphs earlier.
Funny how the penalty numbers do all the persuading. Every landing page lesson in one product: the state of Florida wrote my value prop for me.

You've named the real business, yeah. The checker is a demo; the asset is a rules table that's correct, and the liability is a rules table that's stale. A wrong deadline isn't a bug, it's the exact harm the product exists to prevent — worse than no tool at all.
How I'm handling it, honestly at small scale:
Every rule row carries a "last verified" date and a source, and that date shows in my data — nothing ships unverified. All 10 states live in a single source of truth, so an update happens in exactly one place. The reminder design itself is the safety margin: paid alerts fire at 90/60/30/7 days, so even if a state shifts a date by a few weeks, users get warned far ahead of any cliff. Fee/penalty changes mostly come out of legislative sessions, which cluster in spring — so re-verification is scheduled around when changes actually happen, not an arbitrary calendar. And the checker states its verification date rather than pretending to be infallible.
The trap framing cuts both ways though: the reason this data goes stale everywhere (state websites included, sometimes) is that maintaining it is tedious. Tedious-but-critical is exactly what a solo operator with low overhead can be better at than a big competitor with 50 products, because for me it's the whole job. If I ever start dreading the verification pass, that's the signal the business has outgrown the approach — and by then there should be revenue to solve it properly.
Appreciate you saying the quiet part. It's going in the operating doc.

Thanks — that's exactly the shift. The thing that made it click for me: the moment of pain has a timestamp. Nobody wakes up wanting deadline software; they want it the day they get a $400 notice, or the night before they think something's due. Search is the only channel that's present at that exact moment. Communities like this one are where I learn how to build the thing — but the customer is mid-Google, not mid-scroll.
The nice side effect is it disciplined the roadmap too: every feature now has to answer "does this help the person who just searched their problem?" Cuts a lot of nice-to-haves.