Hybrid journals are subscription journals that charge an extra fee to make a specific article open access while the remainder of the journal remains behind a paywall. This type of gold open access is always accompanied by a fee. This fee is called an article processing charge (APC).
A number of funders (such as Wellcome Trust, RCUK/UKRI, and Gates) no longer support the direct costs of publishing in hybrid journals, which means that we cannot use our block grants to pay APCs for hybrid journals where authors are funded by Wellcome or RCUK/UKRI. Where a funder has an open access mandate that requires immediate open access, authors investigate whether there is a Read & Publish deal that they can use, and if not, use rights retention instead.