Age play - One or more consenting adult characters role playing, pretending to be babies or children. Most retailers will take this, but iBooks will not.
Bestiality - Sexual relations between humans and real-world animals (sex with Big Foot, dinosaurs, shape shifters and other imaginary creatures is not bestiality). Few retailers will take this.
Dubious Consent (dubcon) - A common and popular theme in mainstream fiction. Dubcon explores the gray area between consent and non-consent. Not clear if the receiver of the sexual act was fully on board or not at the time of the act. Most retailers will take this.
Incest or pseudo-incest - Sexual relations between family members, whether biologically or non-biologically related. Includes stepbrother, stepsister and step-anyone. Few retailers will take this.
Nonconsensual sexual slavery - Erotic depiction of a person captured or held against their will, such as kidnapping, imprisonment or human trafficking. Not to be confused with BDSM, which is predicated upon informed consent and negotiation between both parties before the act, and which provides safe words so either partner can end the act if it goes too far. If the book adheres to BDSM best practices, do not classify it as Nonconsensual sexual slavery. Few retailers will take nonconsensual sexual slavery.
Rape for titillation - The dominant theme of this book is rape — whether the rape is by one person or a character is raped by a group of people, i.e. a gang rape or nonconsensual "gang bang" — and it targets readers who are titillated by the fantasy of nonconsensual sexual relations. Few retailers will take this.
Others not mentioned - The above list is not all inclusive. There are many other taboo themes that have never been allowed at Smashwords or our retailers (underage erotica, snuff, scat and necrophilia, for example). For a full summary of Smashwords erotica policies, please review Section 9f of the Smashwords Terms of Service.