Look at the pan
From a normal viewing position, note a steady trickle, rippling or water movement after the flush should have finished.
Continuous water may be heard at the cistern, seen entering the pan or noticed as repeated refilling. Capture that pattern without removing the cistern mechanism.
Keep the toilet out of repeated use while you note the visible or audible sequence.
From a normal viewing position, note a steady trickle, rippling or water movement after the flush should have finished.
Record whether filling continues steadily, stops and restarts, or never seems to finish.
A rough description such as constant or intermittent is enough.
See Toilet Repair for continuous running, refilling or a cistern mechanism concern. If pan water rises or waste drains slowly, see Blocked Toilet instead.
Add what happens after a flush and whether the continuing sound or movement is constant or intermittent.
A clear message helps a plumbing professional understand the next step.