Keep the old way running

The riskiest moment in replacing a manual process is the day you switch it off. Whatever the old way caught without anyone noticing, a person double-checking a total or remembering that one customer always orders in cases, stops being caught.

So we don't switch it off. The new system runs next to the old one, on the same real work, and we compare what each produces.

What running in parallel looks like

Say a team enters purchase orders from a shared inbox by hand. While we build, they keep doing exactly that. The new tool reads the same emails and prepares the same entries, but it doesn't post anything. Every day we compare the two:

• Where they agree, we gain confidence.
• Where they differ, someone looks at why. Usually it's an exception nobody had written down, and the tool learns to handle it or to hand it to a person.
• Where the tool isn't sure, it says so, and that becomes a case it routes for approval.

When the differences stop being surprising, the team moves over one piece at a time, and the old way stays available until nobody reaches for it.

Why it's worth the extra weeks

Running in parallel takes longer than a hard cutover, and it means the team does the work twice for a while. In return, the switch happens on evidence instead of on a date. The people doing the work see the new system get things right on their own cases before they rely on it, which matters more for adoption than any demo.

It also produces the most useful document a project can have: a list of every exception the business really has, and what happens to each one.