Lays a charge

Spell effects, and occasionally supernatural abilities, can sometimes lay a charge, either on their target, or on the caster who cast the spell or used the ability. When something lays a charge, it either affects the subject with an Arcane Bonus, a Divine Bonus, or a Dual Charge bonus. The term lays a charge refers to the fact that one of these bonus types is now in use by the subject, usually because they were the recipient of some buff effect. As a result, subsequent effects that would apply the same bonus type will not stack, even if they are attempting to adjust totally different character attributes. As soon as a new charge is placed upon your character of the same type as an existing charge, you must immediately either choose to replace your existing charge with the new one, or keep your existing charge.

Effects that lay a charge don't work the same way as normal bonus type stacking. Normal bonus types can't be stacked with themselves, but only if they're trying to affect the same character attribute (for example, you can't add together two different enhancement bonuses that improve your armor class; you can only have one enhancement bonus affecting a given character attribute). You can have two enhancement bonuses, as long as they are being applied to different attributes (i.e. one is boosting AC, and one is boosting to-hits).

When a spell or ability lays an Arcane Bonus (for example), you cannot get a second Arcane Bonus applied to you for any reason, even if both charges affect totally different attributes. You can only have one, regardless of which attributes they are affecting. The same is true of Divine Bonuses. However, you can have an Arcane Bonus and a Divine Bonus present at the same time, even if they are both affecting the same character attribute. The exception to this rule is you cannot get two versions of the same buff spell (i.e. that share the same spell name, like Stoneskin (Druid Spell) (which lays a divine bonus) and Stoneskin (Sorcerer/Wizard Spell) (which lays an arcane bonus); these cannot be stacked, even though they lay different bonus types).

A Dual Charge overwrites both the Arcane Bonus and the Divine Bonus at the same time, assuming you accept it, meaning if you have an effect on you which lays a Dual Charge, you may not accept any effects which Lay and Arcane, Divine, or Dual Charge, unless you overwrite your existing Dual Charge effect.