It should be centralized under a single Business Systems teams with the rest of your internal tools.
Siloed Business Systems is the left hand not talking to the right.
It’s the Sales Systems team making decisions about tools that touch Deal Desk and Billing without taking Finance into account.
It’s the Customer Support team making decisions about Call Center tooling without thinking through the end-to-end customer journey and handoff from Sales.
When Internal Tools live within the individual business units, those teams inevitably prioritize their needs and think about the impact change will have on other teams secondarily.
(And anyone who says a healthy, cross-functional collaboration prevents these issues is kidding themselves.)
A siloed approach to Internal Tools creates a fragmented customer experience and leaves huge gaps in data visibility.
On the other hand, centralized Business Systems lead to a cohesive, intentional, and proactive strategy that accounts for the 30,000 foot view of what the entire business needs (now and in the future), while also taking the tactical execution and day-to-day support off the plate of individual business units.
The biggest mistake I see companies make is thinking that centralizing Business Systems only makes sense when you reach maturity.
In reality, as soon as 2+ teams have dedicated Internal Tools headcount, the team should sit under a unified Systems Leader.
A challenge in the dynamic of moving from siloed to centralized is that key stakeholders feel that something they once controlled is being taken away.
In reality, ownership of Internal Tools is simply being moved in order to better serve those stakeholders and their teams.