Sunset the old way on purpose.
As long as the old way still works, the new way is optional. Adoption that holds usually requires deliberately closing the door behind you.
Most rollouts introduce the new way and leave the old way running. It feels prudent. Keep the legacy system available as a fallback, let people transition at their own pace, avoid the disruption of a hard cutover. It also, quietly, guarantees that adoption will stall.
As long as the old way still works, the new way is optional, and optional change is the change people opt out of the moment it becomes inconvenient. Every time the new process is unfamiliar or slow, and it always is at first, the old path is right there, comfortable and functional. Under pressure, people take it. Not out of resistance, but out of rational preference for the tool they already know.
The parallel-running trap
Running old and new in parallel seems to reduce risk. In practice it does the opposite, because it removes the forcing function that adoption depends on. The organization ends up maintaining two systems, splitting its data and its habits across both, and never fully committing to either. The new way never reaches the critical mass where it becomes the default, because the old way keeps siphoning off exactly the moments when commitment would have been built.
The transition that was supposed to be gradual becomes permanent. Years later, a meaningful share of the work still runs on the legacy path, the promised benefits of the new system never fully land, and everyone has quietly accepted a half-migration as the steady state.
If the old way still works, you have not deployed a new way. You have added an option that most people will decline under pressure.
Closing the door is a design decision
Anchoring a change often requires deliberately removing the alternative. That means setting a real date after which the old system is turned off, the old process is no longer accepted, the old form is no longer processed. Not as a punishment, but as the mechanism that converts an option into the way things are done.
This has to be designed, not improvised. It requires being genuinely ready, the new way actually working, the people actually able to use it, before the door closes, because closing it on an unready organization is reckless. But once readiness is real, the deliberate sunset is what turns a hopeful rollout into an accomplished one. The clarity is a gift: when there is no fallback, the organization stops hedging and commits.
Readiness first, then the cutover
The sequence matters enormously. Sunsetting the old way before people are ready to succeed on the new one creates chaos and breeds exactly the resentment that dooms a change. The old way is a safety net, and cutting a safety net before anyone can walk the wire is not decisiveness, it is negligence.
So the honest version of this discipline has two parts. First, do the readiness work, the desire and the ability, until the organization can genuinely operate the new way. Then, and only then, close the old path deliberately and on a known date. The first part earns the right to do the second. Skipping the first is how forced cutovers become disasters, which then get cited as reasons never to force a cutover again.
Reversion is the default without it
Change reverts. It is the natural tendency of any organization to drift back toward the familiar the moment the attention of the transformation lifts. Reinforcement fights that drift, and one of the most powerful forms of reinforcement is simply the absence of the old road. You cannot drift back to a path that no longer exists.
This is why the deliberate sunset belongs to the anchoring work, not the launch. The launch introduces the new way. The sunset is part of what makes it survive. A change that leaves the old way open has left itself an exit, and organizations under pressure use every exit they are given.
Decide the date on purpose
When you plan a rollout, plan the ending of the old way with the same seriousness you plan the beginning of the new one. Decide, in advance and out loud, when the fallback closes and what readiness has to be true before it does. Left undecided, the old way runs forever, and the transformation you paid for stays permanently optional.