It is the first question most business owners ask, and the answer people want is a number. The honest answer is that it depends, and the useful part is understanding what it depends on.
Why there is no fixed timeline
Search engines do not publish a schedule. Changes you make have to be discovered, processed and weighed against everything else competing for the same searches, and that happens at different speeds for different sites.
Anyone who promises a specific ranking by a specific date is guessing or selling. A credible agency will talk about ranges, leading indicators and the factors below.
What affects how quickly SEO works
Competition matters most. A search with a handful of weak results moves faster than one dominated by established national brands.
The starting point matters too. A site with serious technical problems can see improvement soon after those are fixed, while a brand new site has to earn trust from nothing.
Your resources shape the pace: how quickly changes can be implemented, how much good content you can produce and whether the site can earn links and mentions from reputable places.
What usually happens first
Early progress tends to show up in places other than rankings. Pages get crawled and indexed properly, technical issues disappear from reports and impressions begin to rise for more relevant searches.
Those signals are worth tracking because they come before clicks and enquiries. They show that the foundations are working even when the headline numbers have not moved yet.
How to judge progress sensibly
Agree measures that matter to the business, such as qualified enquiries, calls and revenue from organic search, and review them over months rather than days.
Be wary of reports that celebrate rankings for terms nobody buys with. Visibility is only valuable when it connects to something your business wants.