A few months ago, a logistics company I work with needed its business plan finished — a plan built around a funding ask, so every number in it had to hold up to an investor's scrutiny. There was one problem. The revised working files were gone — not in the shared drive, not in email, not anywhere we looked.
We rebuilt the entire plan anyway. And the finished numbers landed within about 2% of the figures we had approved months earlier. The only reason that was possible is something unglamorous: a decision log.
What a decision log actually is
A decision log is a running note of the choices you make while building something — and the reasoning behind each one.
It is not the file itself. It is not a backup. It is the short paper trail that says what you decided and why.
For this plan, the log held things like:
- We cut the funding target and reworked the forecast around the smaller number.
- We changed which revenue lines launched first, and in which months.
- We moved the break-even timing based on real cost assumptions.
None of that is the spreadsheet. But it is enough to rebuild the spreadsheet.
Can you really rebuild a plan from a few notes?
This is the part most owners doubt, so here is the honest answer: yes, if the log captured the decisions rather than just the results.
A lost file takes the numbers with it. But numbers are downstream of choices. If you know the choices — the funding figure, the margins per service line, the launch order, the tax rate — the numbers can be built again.
That is exactly what happened. We reconstructed the forecast from the logged decisions, and the rebuilt version matched the old approved one closely enough to trust. The work that had to be redone was small. The thinking never had to be redone at all.
What to write down (and what to skip)
You do not need a fancy system. A dated note, a shared doc, or a pinned message thread all work. The trick is writing the right things.
Capture the decision, not the discussion
Skip the back-and-forth. Log the outcome: "We set the budget at X because Y." One line per real decision.
Always include the "because"
A decision without its reason is half a decision. When you rebuild later, the reason is what lets you re-derive everything downstream.
Log it the day it happens
Memory fades fast. A choice you made three weeks ago is already fuzzy. Write it down while it is fresh, not when you finally get around to it.
Why this beats relying on backups alone
Backups protect the file. A decision log protects the thinking — and the thinking is the expensive part.
Files get lost in ways backups miss: a folder someone moved, a version that never synced, a document that lived on one laptop. When that happens, a backup you don't have is worthless. A decision log you kept turns a disaster into an afternoon of rework.
There is a second payoff, too. Every figure in the rebuilt plan arrives with the reason it is what it is — the funding number, the margins, the launch order. When someone eventually asks why, the answer is already written down. The log wasn't just insurance. It was proof of a clear head.
The takeaway: your files are worth protecting, but your decisions are worth even more — write them down as you go, and you'll never truly start from zero. Next time you make a real call in your business, spend thirty seconds logging what you chose and why.