This is usually handled much more elegantly by senior academic staff.

You contact a department who’s services you use a lot, then you arrange to pre-pay for services. Ideally you negotiate a discount.

Then you use the service and state which grant to draw from.

This way you have grants paying for things that are completely unrelated to their intent, you have one nightmare of a billing system which no one understands and you get to use everybody cent.

This as a fairly recent occurrence in my research group. It’s often quite tedious because you don’t want to waste the money and it’s never clear if there’s going to be a period where we’re short on cash at some point in the future. most of it’s spent on boring but expensive things to be used down the line. Would be far better if funding wasn’t quite so cyclical!

Could you order conference tickets or something similar that allows free cancelations in the future? In my previous job, we did this to carry over training budgets.

Buy annual licenses. Then renew if you want to block the same amount next year OR don't renew and use it for what you actually need.