Stop Carrying Stale Assumptions: Give Your Development Evidence an Expiry Date

You checked the planning controls three months ago. The builder's estimate came from an early sketch. Comparable sales were current when the site first appeared. Because each item was once researched, it is easy to keep treating it as true.

A capable developer asks a harder question: is this evidence still fit for the decision being made today? Evidence can become stale as design, timing, prices, authority requirements and project circumstances change.

Use the DATE control

1. Describe: record exactly what the assumption says and which decision relies on it.
2. Authority: identify the source, author, jurisdiction and limits.
3. Time: record when it was obtained and a sensible review date.
4. Event: name the trigger that forces an earlier recheck, such as a design change, delayed settlement or revised scope.

Australian Government risk guidance supports assigning responsibility, monitoring controls and reviewing a risk plan. NSW pre-lodgement guidance encourages early checks of planning controls and site constraints. Neither makes evidence permanent.

A clearly labelled hypothetical

A feasibility uses a six-month-old civil allowance based on three townhouses. The concept now contains four. Rather than increasing the allowance by guesswork, the developer marks it expired, asks the engineer to confirm the changed scope and holds the acquisition gate until the consequence is understood.

Set expiry by consequence

A low-impact desktop observation may survive until the next review. A planning interpretation, finance term, service capacity statement, construction price or legal position supporting a major commitment deserves a deliberate review date and specialist confirmation. The higher the consequence and the faster the input can change, the shorter the review interval should be.

Do not create false precision by giving every item the same expiry. Link review frequency to consequence, volatility and the next irreversible decision. Requirements vary by site and jurisdiction.

The Think Property Club System makes assumptions visible. Specialists refresh evidence within their competence, while Support helps challenge the comfortable phrase, “we already checked that”.

Your next action

Choose the ten assumptions carrying your current feasibility. Add source date, owner, next review date and early-review trigger to each one.

Key Takeaway

Due diligence is not finished when evidence is collected; it remains useful only while its age, scope and authority still match the decision.

Your Turn

Which assumption would hurt your deal most if it quietly became outdated this week?

Continue learning

• Evidence confidence register
• Development decision log

Sources and boundaries

1. Australian Government, Make a risk management plan (current page; accessed 9 September 2026)
2. NSW Planning, Stage 1 – Pre-lodgement (current page; accessed 9 September 2026)

This article is general education, not personalised planning, legal, financial, tax or building advice. Requirements and outcomes vary by jurisdiction, site, contract, structure and circumstances. Check current information with the relevant authority and appropriately qualified advisers.