Is Plan S Open Access Working? A Sceptic’s Case for Differentiated Mandates

• What Plan S Actually Requires
• The Case Against the Blanket Mandate
• cOAlition S’s Own Retreat From Rigidity
• Common Questions About Plan S
• Toward Differentiated Funder Mandates
• Conclusion: What Should Come Next

Five years on from its 1 January 2021 compliance deadline, Plan S open access policy sits in an odd position: widely credited with putting open access on every funder’s agenda, yet quietly walked back by the very coalition that wrote it. An independent October 2024 review, Galvanising the Open Access Community: A Study on the Impact of Plan S, found the policy had a “game-changing” effect through its Rights Retention Strategy. But cOAlition S’s own 2026–2030 strategic plan tells a second story — one of phased retreat from the rigid, one-size-fits-all mandate it launched in 2018. That gap between celebratory retrospective and quiet course-correction is the real story, and it is worth asking plainly whether a blanket mandate was ever the right instrument.

What Plan S Actually Requires

Plan S was launched in September 2018 by cOAlition S, an international consortium of national research funders and charitable foundations that includes UKRI and the Wellcome Trust. Its ten founding principles required that, from 2021, all peer-reviewed publications resulting from funding by coalition members be made immediately open access — either in a fully open access journal or platform, or via deposit in an open repository with no embargo.

Two mechanisms did the heavy lifting:

• The Rights Retention Strategy (RRS), which lets funded authors apply a CC BY licence to their author-accepted manuscript regardless of the publisher’s own policy, enabling immediate green open access.
• Article processing charges (APCs), the fee-based gold open access route, which cOAlition S initially agreed to fund on authors’ behalf where a compliant venue existed.

Notably, the original ten principles were scoped to peer-reviewed journal articles and conference proceedings. cOAlition S explicitly deferred a firm mandate for monographs and book chapters, citing the different funding cycles, peer-review norms, and licensing conventions of humanities and social-science (HSS) publishing — an early acknowledgement that a single rulebook does not fit every discipline.

The Case Against the Blanket Mandate

The criticisms of Plan S are not new, but they have hardened rather than faded. Three stand out.

Cost-shifting to APCs. By pushing gold open access as the default compliant route, Plan S moved the cost of publishing from reader-side subscriptions to author-side fees. Well-resourced institutions and grant-rich disciplines absorb this easily; early-career researchers, unfunded scholars, and institutions in lower-income countries do not. Critics — including Science (AAAS), in its 2024 “mixed review” of the policy — have argued this risks a pay-to-publish stratification that Plan S was meant to dismantle, not recreate.

Disciplinary disparities. STEM fields, with large grant budgets and a journal-article-centred publishing culture, adapted to Plan S’s timelines relatively smoothly. Fields with smaller grants, more diffuse funding, or monograph- and edited-volume-centred outputs did not. A mandate calibrated to biomedical and physical-science funding flows does not transfer cleanly to a discipline where the primary scholarly output is a single-author book written over several years.

The humanities and monograph fit problem. Books remain the primary currency of career advancement in much of the humanities. Open access book publishing carries different cost structures (often higher per-unit costs than a journal article), different licensing sensitivities (image rights, third-party permissions, translated quotations), and a much thinner diamond and institutional-press ecosystem to absorb the volume. Applying a journal-shaped policy to a book-shaped discipline was, on the evidence of cOAlition S’s own deferred treatment of monographs, recognised as a mismatch from the outset — yet the underlying tension has never been fully resolved.

cOAlition S’s Own Retreat From Rigidity

What makes the sceptic’s case harder to dismiss is that cOAlition S has, in effect, conceded much of it. The coalition’s published strategy for 2026–2030 signals a deliberate shift away from the rigid instruments of the 2018 launch:

• Support for transformative agreements — once framed as a transitional bridge to full open access — is being wound down, an implicit admission that offsetting deals entrenched incumbent publishers’ revenue rather than transforming the market.
• The strategy explicitly states that “no single model can meet all needs”, formally endorsing a plurality of routes (green, diamond, community-owned platforms) instead of privileging APC-funded gold.
• Diamond open access — non-APC, non-subscription publishing typically funded by consortia, learned societies, or institutions — receives markedly more strategic weight than it did in 2018, partly because it fits humanities and society-publishing contexts that APC-gold never did.
• Implementation timelines and compliance routes have been extended and softened repeatedly since 2021, a pattern of flexibility that was largely absent from the original ten principles.

None of this is framed by cOAlition S as a repudiation of Plan S. But read against the criticisms above, it is difficult to interpret the 2026–2030 strategy as anything other than a coalition adjusting a blanket mandate toward the differentiated approach critics have been requesting since 2018.

Common Questions About Plan S

What is Plan S in open access?

Plan S is an open access mandate launched in 2018 by cOAlition S, a coalition of national research funders including UKRI and the Wellcome Trust. It requires that peer-reviewed outputs from coalition-funded research be made immediately open access on publication, either through a compliant journal or platform, or via a no-embargo repository deposit.

Do I have to pay for open access?

Not necessarily. Gold open access typically involves an article processing charge (APC) paid by the author or funder. Green open access via repository deposit and diamond open access (no author or reader fees) are both compliant, fee-free alternatives that Plan S — and increasingly cOAlition S’s own strategy — actively supports.

Toward Differentiated Funder Mandates

The evidence points toward a specific policy design failure rather than a failure of open access as a goal. A single compliance clock, a single funding assumption, and a single default route (APC-gold) were applied across disciplines with radically different publishing economies. The fix is not to abandon open access mandates but to differentiate them:

• Route-neutral compliance that treats green, diamond, and gold as equally valid by default, rather than gold-as-default with green as an exception.
• Discipline-aware timelines, recognising that a monograph-based field cannot realistically match a journal-article field’s production cycle.
• Direct funding for diamond infrastructure in HSS fields, rather than expecting APC markets to develop where publishing economics do not support them.
• Transparent reporting on cost-shifting, so funders and institutions can see whether a mandate is redistributing cost fairly or simply moving it from library budgets to grant budgets.

For research administration teams managing funder compliance day to day, this is not an abstract debate — differentiated mandates mean different checklists, different budget lines, and different risk profiles by discipline, and institutional policy needs to reflect that variation rather than applying one open access rulebook across every faculty.

Conclusion: What Should Come Next

Plan S succeeded at the one thing a blanket mandate is good at: forcing the issue onto every funder’s and publisher’s agenda within a few years, where voluntary encouragement had achieved comparatively little in the preceding two decades. It failed, or at least strained badly, at the thing blanket mandates are structurally bad at — accommodating disciplinary and economic diversity. cOAlition S’s own 2026–2030 strategic pivot toward plural, discipline-flexible routes is the clearest evidence that the coalition has reached the same conclusion. The sensible reading is not “Plan S failed” or “Plan S succeeded”, but that the next generation of funder mandates should be designed as differentiated instruments from the outset, rather than retrofitted into flexibility five years after a rigid launch.