Canceling IFR During Approach

The preferred moment to request IFR cancellation is during the approach, once you have established visual contact and are within a few miles of the aerodrome. ATC will approve your cancellation request and may ask you to report again once you have landed (to confirm the aircraft is on the ground and no longer occupying the approach airspace).

Requesting IFR Cancellation on Final Approach

Munich Tower · D-KLMN

PILOT: Munich Tower, D-KLMN, final runway 08 left, visual with runway, requesting cancellation of IFR.
ATC D-KLMN, cancellation APPROVED, report landing complete.
PILOT: WILCO, report landing complete, D-KLMN. [... landing occurs ...]
PILOT: Munich Tower, D-KLMN, landing complete runway 08 left.
ATC: D-KLMN, ROGER, CONTACT ground one-two-one decimal nine.