Q. Can a receptacle be used as a splicing device? In other words, can we use all four screws (hot and neutral) on the receptacle?
A. Yes. However, continuity of the neutral conductor of a multiwire branch circuit must not be interrupted by the removal of a wiring device [300.13(B)]. In these applications, the neutral conductors must be spliced together and a "pigtail" provided for the wiring device. The opening of the ungrounded conductors, or the neutral conductor of a 2-wire circuit during the replacement of a device, doesn't cause a safety hazard, so pigtailing of these conductors isn't required [110.14(B)].
Caution: If the continuity of the neutral conductor of a multiwire circuit is interrupted (opened), the resultant over- or under-voltage can cause a fire and/or destruction of electrical equipment.