Day 1 is the entity’s first day under its new flag: new governance, sometimes a new name, and above all a new IT environment. It is the day every employee must be able to log in, send an email, reach their applications and get paid at the end of the month. Here is the Day 1 checklist: the control points that separate a successful Day 1 from a black Monday.
Before: what must be ready and rehearsed
Identities first. Every employee in scope has a working account in the new environment, tested, with their application access rebuilt. Email next: mailboxes migrated or redirected, history accessible, signatures and aliases in place. Then the critical applications: a list validated with the business lines, end-to-end tests, and a fallback procedure for each. Payroll and HR remain the most socially sensitive point. You therefore lock them down with a full test cycle. Finally, the dress rehearsal. Indeed, a Day 1 is not attempted, it is rehearsed, with a timed scenario and clear go / rollback criteria.
During: a control tower, not an inbox
On the day itself, you need an identified command cell. Concretely, that means a single point of contact for incidents, a running log of events, status updates at fixed times, and designated spokespeople for internal communication. Indeed, the first days concentrate small-scale incidents: a forgotten access, an orphaned printer, a missing shared folder. Thus, how fast they are resolved shapes how the whole deal is perceived.
After: stabilize, measure, document
The following week is for stabilizing. First, clear the incident queue. Then, measure: successful login rate, tickets opened and closed, applications operational. Finally, document what deviated from the plan. Indeed, these lessons feed directly into what comes next: the following migration waves and the TSA exit.
Day 1 checklist: the takeaway
A successful Day 1 is not a lucky day. It is the result of a tested separation plan, locked-down identities and a prepared command cell. We have condensed this Day 1 checklist into a PDF your CIO or integration manager can use as is. It is available free on the homepage.