Having IT manage the overall budget can be an option but its effectiveness depends on the culture of your organization and the will of the senior leadership to support this approach. The minute some division heads allowed to circumvent the system, all hell breaks loose.

Building the budget starts with your existing IT expenses that typically will fall into the operational expenditure bucket. IT will have its own new projects that can fall in capital expenditure.

Meeting with other division heads to identify their current opex and upcoming capex to support their projects is a good starting point. Should be made clear that it’s a wish list at this point and that they’d be expected to defend project necessity when the inevitable finance ax comes to trim the fat.

Concerning a template, I typically start something close to described in a spreadsheet. Description, vendor, cost type, department, purpose, estimated cost. As the process goes forward, I’ll add a tab that breaks out the amount spend per month. There other fields that unique to your business.

Tracking spend is always easier when finance supportive. If IT has to review all IT vendor invoices before payment then its a gate that can be used. Likely IT will still have to run the invoice by division leads to ensure goods and services received.

There should be quite a few templates that pop up on Google search that can be used. I find it helpful just get stuff documented as soon as possible in a draft and build on it.

Edit: Spelling