The proof trail method
Five stages from one budget line to a plan someone else can check.
The method takes about an afternoon for a single line and a season for a whole plan. Each stage produces a short, durable note. Together the notes form a trail that another person can follow without asking you what you meant.
Stage one
Claim: say what the line is for
Write the line as one sentence that says what the money is for. "Groceries for the two adults in the household, agreed each month" is a claim. "Food" is only a category, and a category without a sentence cannot be checked. Keep the claim short enough to fit on a sticky note. If you cannot finish the sentence, the line is probably two lines pretending to be one.
Ask yourself:
- What exactly does this figure cover?
- What does it leave out on purpose?
- Who agreed to it, and when?
Stage two
Source: name the record behind the figure
Name the record the figure rests on: a statement, a receipt, an invoice, a signed agreement, an email that confirms a price, or a dated note from the person who made the decision. If several records apply, list the strongest first. If there is no record, say so plainly, for example: "Estimate based on recent months, not yet compared with statements." An honest estimate is still a useful line in a trail.
Ask yourself:
- Which record would change my mind if it disagreed?
- Is the source in my own hands, or held by someone else?
Stage three
Date: record when the basis was made and checked
Attach two dates. The first is the date the source was created. The second is the date you last compared the figure with it. They are different. A bill can be accurate for the period it covers and still tell you nothing about the next period. Write both dates in the same format every time, so the trail sorts cleanly when you read it back.
Ask yourself:
- Is the source still current?
- When did I last check it, and who checked it?
Stage four
Test: run one check someone else could repeat
Choose one check that someone else could repeat. For example, collect the last few statements that cover this category, add up the matching transactions and compare the total with the planned figure. Then write down how close is close enough for your purposes. The test does not need to be clever. It needs to be written down so that it can be run again. Record the result, including a result that disagrees with the plan.
Ask yourself:
- What would I need to see to conclude that this line is wrong?
- What tolerance did I accept, and why?
Stage five
Revisit: schedule the next look
Set a review point. It can be a date on a calendar, a change in circumstances or the end of a contract. When you revisit, do not rewrite the trail. Add a new dated entry beneath the old one. A trail that keeps its history is more trustworthy than one that looks freshly tidy, because you can see how the plan actually changed.
Ask yourself:
- What event should trigger the next review?
- Who is responsible for writing the next entry?
A worked example in words
A line for planned travel
Consider a planned line for household travel. The claim is "Transport and lodging for the planned trips, as booked or as estimated." The source is a booking confirmation for each trip that has one, and a written estimate, labelled as an estimate, for each trip that does not. The first date is the date each confirmation was issued and the date the estimate was written. The test compares the confirmation totals with the line once the bookings are final. The revisit is set for the week before the first trip, when each estimate should either become a confirmation or be changed with a dated note.
This example shows the shape of a trail. It is not a recommendation about what to spend.
When the trail breaks
Record failures instead of hiding them
Sometimes a test fails. The line is too low, a contract changed, or a record cannot be found. Do not hide the failure. Write it in the trail as a dated entry with the new figure, the reason and the person who agreed to the change. A broken link that is recorded is far more useful than a smooth chain that was quietly patched.
A note on scope
This method teaches record keeping. It is not financial, legal, tax, or medical advice, and it does not predict prices or recommend any particular spending or investment. Where a decision has real consequences, ask a qualified professional who can see your full situation.