Validation means finding evidence that a specific group of people has a problem they care about and would act to solve. It is cheaper to learn that before you build than after.
Start with a narrow customer
"Small businesses" is not a customer. "Solo bookkeepers who send invoices by hand" is. The narrower the group, the easier it is to find them, talk to them and write something that speaks to them.
Talk to ten people
Short conversations beat surveys at the start. Ask about their last experience with the problem, not whether they would buy your idea.
- What did you do the last time this came up?
- What did you try, and what was frustrating about it?
- What does it cost you in time or money today?
Write down their words. Patterns in repeated phrases are your best copywriting.
Run a small demand test
Put up a one-page site that describes the offer and collects email addresses, or ask people to pre-order or join a paid pilot. Sharing the page in the places your customer already gathers gives you a signal. Interest from friends and family does not count.
Decide honestly
Set your bar before you look at results, for example the number of conversations that described the same problem. If you clear it, continue. If you miss, change the audience, the problem or the offer, or stop. Stopping early is a valid result and saves months.