Report outcomes rather than activity. Meals served is activity. People who no longer skip meals is an outcome. Trees planted is activity. Acres restored and surviving after three years is an outcome. The second version is harder to produce because it requires measurement over time, which is precisely why it carries weight when everybody else is publishing the first version. If you can only report activity honestly, report activity honestly rather than dressing it as impact.
Use numbers with denominators. A figure on its own is unreadable: two hundred people helped means nothing without knowing whether that is most of the need or a fraction of it. Two hundred out of an estimated eight hundred in the county gives a reader the shape of the problem and your place in it. It also makes the case for continued support more clearly than any appeal, because it shows work remaining.
Show individual cases alongside the aggregate, because the two do different jobs. The number establishes scale and the story establishes that the number describes real people. One specific account with a name and details, used with genuine permission, will be remembered when the figures are not. Publishing both together avoids the two common failures, which are statistics nobody feels and anecdotes nobody can generalise from.
Publish on a fixed schedule and include what did not work. An annual report that only contains successes reads as marketing, and readers discount it accordingly. Naming a programme that underperformed and what you changed is the single strongest credibility signal available, and almost nobody does it.
Report on a fixed schedule rather than when there is good news, because selective timing is visible over a few years and it undermines everything published. An annual summary that appears at the same point each year, whether the year was strong or difficult, reads as accountability. One that appears only after a successful campaign reads as marketing, and readers who notice the pattern discount the successful years too.
Be precise about attribution, which is where impact claims most often overreach. If your programme was one of several factors, say so rather than claiming the outcome. If the change would have partly happened anyway, acknowledge it. Overstated attribution is the specific failure that damages credibility with the funders and partners who understand the subject best, and those are precisely the readers who matter most for a mission driven organisation.