What is an Article Processing Charge (APC)?
One of the new business models supporting open access to journal articles is an author‐side payment to the publisher of a processing fee to publish accepted articles. This fee is called an Article Processing Charge or APC. A consequence of paying an APC is gold open access, i.e., open access to the published article on the publisher’s website. All hybrid journals and some open access journals levy an APC. (Open access journals that do not require payment of an APC are subsidized by the hosting university or scholarly society, funded by philanthropy or institutional memberships, or funded by a combination of revenue streams.)
Typically APCs are paid by the author’s sponsor (funding agency or employer) and waived in cases of economic hardship. Few APCs are actually paid by the author, though practice varies across disciplines. Many funding agencies approve of grant funds being spent on APCs to publish open access. See Solomon and Björk (2011), Publication Fees in Open Access Publishing: Sources of Funding and Factors Influencing Choice of Journal [pdf].