Building cancellation in Inter-War is a server-side operation. The backend verifies planet ownership and queue identity and protects the mutation with a transaction and operation token, so repeated clicks cannot safely refund the same job multiple times.
Which price is used for the refund?
The key rule is that cancellation uses the paid* snapshot recorded when construction started. It is not recalculated from today’s building price after catalog, bonus or universe-rule changes.
Why does that matter?
If configuration changes between start and cancellation, the player cannot exploit the new price to create resources. The backend settles what was actually charged.
What happens to the queue?
Cancellation runs against locked user, planet and queue state. A completed item cannot later be cancelled as an old front item, and replaying the same operation token is rejected.
What exact percentage is returned?
The available implementation evidence safely confirms the paid-cost snapshot model, but not a publishable building-specific percentage. The current server/UI value for the selected universe should be treated as authoritative rather than copying a percentage from research or Shipyard cancellation.
FAQ — building cancellation
Can a later price change alter the refund?
It should not; the operation uses recorded paid* values.
Can the same item be cancelled twice?
Transaction and idempotency protections are designed to prevent that.
Related FAQ: How is building time calculated? · How is resource production per hour calculated?