Do you have to indicate when changing lanes in Northern Ireland?

The Highway Code says drivers should give clear, timely signals before changing direction or lane when a signal will help other road users.

Rule 103 emphasises checking that a signal is not misleading, giving it in good time and cancelling it afterwards. A signal cannot replace mirrors, blind-spot checks or the need to wait for a safe gap. Moving into a lane simply because the indicator is flashing is not permitted. Check behind and alongside, signal appropriately and change lanes smoothly only when clear.