I hesitated to address the and/or topic in my blog category entitled “Funny phrases” but I must say that there is nothing funny about it. In this weblog, I will address the black sheep of ‘our’ (legal and non-legal) writing: and/or.
Do not ever write and/or. It is the metaphor for laziness and vacuous writing.
There is no need to write the ‘slashed combo’, not even for simplification or keeping the text short. First, one drafter imposes on each of the readers the necessity to do the thinking, which the drafter failed to do. Rather, it gives each party the possibility to cherry pick either and or or whichever is the most favourable interpretation. Second, the simplification is that the actual meaning of and/or (namely the choice between either A or B or both) is somehow left to the reader. Rather, the couplet and/or is largely redundant because the word or logically and grammatically encompasses the same meaning. Third, it completely fails to meet the drafting principle of accuracy.
The ICC International Standby Practices contain provisions on the use of and/or in (standby) documents:
1.10 – Redundant or Otherwise Undesirable Terms
b. A standby should not use the term “and/or” (if it does it means either or both).
1.11 – Interpretation of These Rules
c. Unless the context otherwise requires:
(iv) “A or B” means “A or B or both”; “either A or B” means “A or B, but not both”; and “A and B” means “both A and B”;
Or. Typically, it is sufficient to write or, because it captures or both as well. Erroneously only and is meant.
 ICC Publication N° 590, International standby practices (“ISP 98”), included in my International Commercial Law – Source Materials, Kluwer Law International