Most software upgrades are optional in the short term. You can skip a release, wait for the first service pack, and move when the timing suits you. Acumatica’s move to its Modern UI migration program doesn’t work that way. Acumatica has confirmed that 2026 R1 is the last version that supports the Classic UI, and from 2026 R2 onward there is no way to switch an instance back. In October 2026, Acumatica announced that 2026 R2 is now generally available, so this is no longer a date on a roadmap. It is the current release. For businesses that run on a heavily customized ERP, that turns a cosmetic change into an urgent project.
The new interface looks cleaner, and most users will adjust quickly. The real work sits underneath, in the custom and modified screens that many companies have built up over years. This article explains what actually changes, who is exposed, and how to approach the move without disrupting daily operations.
Why this is not a normal upgrade
A normal ERP upgrade changes features and fixes problems while leaving the way screens are built mostly intact. The Modern UI changes the presentation layer itself. Acumatica’s own guidance says most business logic customizations remain unaffected, but UI-specific customizations may require review and validation. In plain terms, the rules your system follows will survive. The screens your people use every day might not.
Acumatica has also been unusually firm about the timeline. Its deprecation notice states that Classic UI cannot be enabled in 2026 R2 or later under any circumstances, regardless of support tier. There is no premium exception and no extension to buy. Any business planning to stay current with the platform has to complete the move.
There is a short tail, but it is not a reprieve. According to Accounting Today’s coverage of the 2026 R2 release, screens that exist only in the Classic UI can still be opened in 2026 R2, but they display a warning that they will be deprecated in the next release. Existing Classic dashboards and pivot tables also remain accessible in 2026 R2, though new ones can no longer be created, and that functionality is removed in 2027 R1.
A browser change arrives before most upgrades do
Even companies with no plans to upgrade to 2026 R2 face a closer deadline. Starting November 17, 2026, Google is removing XSLT support from Chromium-based browsers such as Chrome and Edge, and Acumatica has warned that this change will prevent Classic UI screens from loading in those browsers. For any team still working in the Classic UI, that is a matter of weeks, not release cycles.
Acumatica has shipped fixes for 2025 R1 and later, and issued updated patches in October after a further Chromium change. Cloud customers receive these through Acumatica, but on-premise customers must apply the patch manually before November 17. Versions 2024 R2 and earlier receive no fix at all, which leaves those businesses with two options: upgrade to a supported version or switch browsers, for example to Firefox.
Who is most exposed
Exposure depends almost entirely on how much a company has customized. A business running close to standard Acumatica, with few modified screens, faces a fairly light lift. The change is mostly about training people on a new layout and checking that reports and workflows behave as expected.
Companies with years of custom screens face a different picture. Custom entry forms, modified grids, extra fields wired into approval steps, and screens built by a previous partner who is no longer involved all need to be inventoried and tested. The risk is highest where nobody fully remembers why a screen was changed in the first place, because those are the customizations most likely to break quietly.
Independent software vendors carry a version of the same burden. Any add-on product with its own screens has to be converted too, and its customers will expect that work done before they upgrade, not after.
The rollout detail that catches teams out
Many teams plan to roll out the new interface gradually, starting with a small group of confident users and expanding from there. On Acumatica, that plan runs into a practical limit. The switch between Classic and Modern is made per screen, and it applies to everyone who uses that screen. Users on Acumatica’s community forum have confirmed that there is no native way to let one person use the Modern version of a screen while a colleague stays on the Classic version.
That changes how a rollout should be planned. Instead of phasing by people, you phase by screens. Start with lower-risk, high-visibility screens, confirm they work, train the people who use them, then move to the next group. The most heavily customized and business-critical screens come last, after the team has built confidence with the process.
Timing is critical here. A screen-by-screen rollout is only possible on 2025 R2 and 2026 R1, where the Classic and Modern versions still coexist. Once an instance is on 2026 R2, that switch disappears. The phased rollout, and therefore, has to happen before the upgrade, not after it. Teams that upgrade first and plan the rollout later lose the safety of moving one screen at a time.
A practical way to approach the migration
The first step is an honest inventory. List every custom and modified screen, who uses it, and what would happen if it stopped working on a Monday morning. This alone often surprises leadership, because customizations tend to accumulate quietly over several implementation partners and many small requests.
The second step is triage. Some customizations will convert cleanly. Some will need rework. Some will turn out to be unnecessary, because the standard Modern UI screen now does what the custom version was built to do. Retiring a customization is often cheaper than converting it, and it reduces maintenance for every future upgrade.
The third step is testing on real workflows rather than on screens in isolation. A screen can render correctly and still break a process, for example when a field that fed an approval rule moves or behaves differently. Acumatica itself notes that some behaviors differ between the two interfaces, such as file upload and time entry format, which is exactly the kind of small change that disrupts a busy team.
There is some good news on timing. According to an Acumatica moderator, the Modern UI architecture was finalized in 2025 R2, with no major disruptive changes planned for the 2026 releases, and customers can upgrade directly from 2025 R2 to 2026 R2. Work done now should not need to be redone later.
When outside help makes sense
For lightly customized systems, an in-house team can often manage the move with Acumatica’s documentation. For heavily customized instances, or for partners responsible for many customer environments, the volume of screens makes tooling and experience matter. Converting hundreds of screens by hand is slow and error-prone, and the deadline does not move.
Specialist programs exist for exactly this situation. A dedicated Modern UI migration program typically starts with a free assessment covering a customization inventory, a scope outline, a compatibility review, and an effort estimate, before any conversion work begins. Development firms such as Sprinterra, which has migrated hundreds of screens across customer projects and its own add-on products, offer either a Modern UI uplift on its own or a full upgrade of the backend and interface together.
The bottom line
The Modern UI is the future of Acumatica, and the Classic UI no longer has a place in it from 2026 R2. Businesses with standard setups can treat the move as a training exercise. Businesses with years of customization should treat it as a project, with an inventory, a screen-by-screen rollout plan, and real workflow testing. Start early, retire what you no longer need, and the switch becomes a chance to clean up the system rather than a scramble against a deadline.
