When UpdateValueEvent is set on PropertyChanged and the mask uses upper/lower token(s) the letters/characters are updated to uppercase after filling the mask. The control should update its text on every key stroke. Update: We are closing this issue because this is expected behavior in MaskedInput. Value property is updated if all required symbols (required from the Mask) are populated. If you need the Value to be updated on every symbol entered you can set the property AllowInvalidValues = True.