Panasonic KX-MC6260E Operating Instructions Manual page 70

8. Programmable Features
Feature/Code
Setting mutual A4/letter print
{#}{7}{7}{6}
70
Selection
This feature allows printing in A4-size even if letter-size recording paper is
installed, and vice versa.
{0} "Off": Deactivates this feature.
{1} "On" (default): Printing is possible between A4/letter-size.