10b5-1 plan
A pre-arranged trading plan that lets insiders sell shares on a fixed schedule, with a cooling-off period, to reduce insider trading risk.
A Rule 10b5-1 plan is a written, pre-arranged plan under which an insider sets future trades in advance, at a time when they do not possess material nonpublic information. The trades then occur automatically, which can provide a defense against insider trading claims. The rules include a cooling-off period before the first trade and disclosure in the company's filings.
On our site, plan-based sales are flagged when the Form 4 footnotes say so. A plan does not reveal the insider's current view, since the decision was made earlier.
Traders care because a plan can explain a sale that otherwise looks like a bet against the company. A cluster of plan sales starting or ending can still be informative.
Worked example (illustrative numbers, not real data): an executive adopts a plan in January to sell 5,000 shares a month starting in April, after the cooling-off period. Sales in April and May are footnoted as made under the plan, so they say less about the executive's view than unplanned sales would.