What is the correct way to present a saving?

For example if I make a saving in this budget period of say £50k, that saving is “permanent” in that I expect to make it next year and so on.

Next year I make a saving in another part my budget of £60k, same as above it is a “permanent” removal of cost

The next year I make a saving of £120k (culmination of a number of expired contracts) which again is “permanent”

So:
Year 1 = £50k saving
Year 2 = £60k saving
Year 3 = £120k saving

Or should I present over 3yrs as
Year 1 = £50k saving
Year 2 = £110k saving
Year 3 = £230k saving

What is the correct accounting method?

how long had the costs been forecast?

Not sure I understand but if I said for example the first £50k had been budgeted for say 3yrs as part of a support contract (3 x £50K say)
I would remove that contract at its expiration anniversary without any new internal charges so the saving is an “actual” £50k. Does that help?

You made a saving and want praise/recognition for it, you won’t get that next year 🙂