Persuasive BriberySource Ultimate Intrigue pg. 88
You know how to get the most out of bribes.
Benefit: You gain a +2 bonus on Diplomacy checks when attempting to bribe someone and on Diplomacy or Charisma checks to bargain with a conjured creature (such as with planar ally or planar binding), in addition to any bonus granted by the bribe itself. The first time someone refuses a bribe you offer, that person’s attitude toward you doesn’t worsen, even if the offer would normally offend the person.