Where does the "apply bonuses and penalties in the most beneficial order" rule come from, if it exists?

Question

I have seen quoted several places on the internet a rule that one can apply bonuses and penalties in the most beneficial order.

An example I come across frequently (as a druid) is the combination of Natural Bond and Alternative Animal Companions. Natural Bond increases your effective druid level for determining the stats of animal companions but cannot increase it beyond your character level. Choosing an alternative animal companion lowers your effective druid level for determining the same stats. The "most beneficial order" rule is used to justify applying the level penalty before the natural bond bonus in order to get around the character level cap on natural bond.

Does this rule actually exist? If so, where does this rule originate? I would like to be able to cite a reliable source for my GM.

Answer 1

It's a "guideline" from the 3.5 FAQ.

As part of an answer to the question

If a monster has resistance and vulnerability to the same kind of damage (such as fire), which effect is applied first? And when does the saving throw come in?"

the answerer (who I think is Skip Williams, but the compiled D&D 3.5 FAQ doesn't specify authors) had this to say:

As a general guideline, whenever the rules don't stipulate an order of operations for special effects (such as spells or special abilities), you should apply them in the order that's most beneficial to the creature. In the case of damage, this typically means applying any damage-reducing effects first, before applying any effects that would increase damage.

... and that's it.

Now, let's make note of a few things.

1. The "guideline" isn't in a rule book. It doesn't cite actual rules. It's a paragraph in an article that lies well outside the main body of rules.
2. The original question had a clearly defined scope, the one of interacting resistances and vulnerabilities. Even though the phrasing of the sentence on its own implies this can be applied in all D&D 3.5 situations ever ("As a general guideline..."), we must not forget its original context.
3. Under no reading is this a hard rule. It's explicitly written as a guideline. Something a GM can reach to to resolve sticky rule situations.

In online discussions, this "rule" is mentioned in all sorts of contexts (a casual Google search for 'D&D 3.5 "most beneficial order"' or similar should reveal dozens of instances). In all but a handful of cases, the text of the "rule" won't be cited. That's because it doesn't exist. "Most beneficial order" is a phrase that haunts online communities.

Does that mean it's useless? No, probably not. It's as good as any other way to do it. You just won't find it in a rule book.

Answer 2

The D20 SRD has this to say about bonuses and penalties, i.e. modifiers:

If the modifiers to a particular roll do not stack, only the best bonus and worst penalty applies

What this means is that if you have two effects giving you armor bonus, for instance, one at +1 and one at +2, then the best bonus, +2, takes effect. Similarly, if you have two competence penalties, one at -1 and one at -2, only the -2 takes effect.

So the better wording would be not that you apply bonuses and penalties in the most beneficial order, but that the highest modifier, speaking as absolute numbers, always takes effect.