Event assumptions register: write down what you are betting on
The plan only works if a dozen things turn out to be true, and nobody has listed them.
The short answer
An assumptions register is a short table of things the plan relies on but has not yet confirmed. Each row has an owner, a way to check it and a date, plus what changes if it proves false.
Assumptions are not risks. An assumption is something you are treating as true now; a risk is something that might happen later. Many risks start life as an unchecked assumption.
Where assumptions hide
- Audience: that members will travel, that the date avoids a rival event or a school holiday, that a senior speaker will draw registrations.
- Money: that the approved figure includes tax and service charges, that a sponsor or grant will arrive before a deposit is due.
- People: that volunteers are free on the day, that the same committee will still be in place in six months.
- Venue and suppliers: that a verbal offer is a booking, that the hall suits the layout you picture.
- Approvals: that a council or board decision will come before a supplier deadline.
How to build the register
- Read the brief, scope and timeline aloud and mark every sentence that starts with we will, they should or it is probably.
- Write each as a plain statement of what is being taken as true.
- Rate it: how sure are we, and how much would it hurt if wrong. Check the high-impact, low-confidence ones first.
- Assign an owner, a way to check (ask the venue in writing, check last year's data, get the minute) and a check-by date.
- Review the register at every committee meeting. Mark each row Confirmed, Changed or Still assumed, and move confirmed items into the plan as facts.
What to do when an assumption fails
Record the new fact in the decision log, then check which scope, budget or date items depended on it. A failed assumption is normal; an unrecorded one is what causes surprise.
If the item touches a specialist matter such as accreditation, safety or legal terms, the owner's task is to put the question to the competent party, not to answer it.
Worked example · Fictional example
A fictional register for a members' conference
Fictional organisation and figures, illustrative only.
A fictional accountants' association plans a two-day conference for 200 to 300 members. Its register has nine rows. One reads: the venue's quoted rate includes service charge. Owner: treasurer. Check: ask the venue to confirm in writing. Check by: before the council approves the budget.
Another reads: 40 volunteers from member firms will staff the desk. Owner: vice-chair. Check: a sign-up sheet circulated at the next meeting. If fewer than 25 sign up, the registration desk scope is revisited.
Use this yourself
Assumptions register
Copy this table into a spreadsheet. The event brief builder also lists assumptions alongside open questions.
| Assumption (what we take as true) | Why it matters | Confidence (high, medium, low) | Impact if wrong | Owner | How and when to check | Status |
|---|---|---|---|---|---|---|
| Still assumed | ||||||
| Still assumed | ||||||
| Still assumed |
Handle it in-house, or bring in help?
Your team can usually handle this when
- The committee is small and meets regularly.
- Most assumptions can be checked with one email or one look at last year's records.
- Someone is willing to keep the register up to date.
Outside planning help earns its fee when
- Many parties, such as co-hosts, venues and funders, each hold part of the facts.
- Key assumptions sit with people who change roles during the project.
- Approvals depend on evidence the committee has not yet gathered.
Want the assumptions checked, not just listed?
An Event Blueprint includes an assumptions and open-questions list built from your brief, with an owner and a check date against each. A project lead can then chase the checks and report which assumptions have turned into facts before decisions depend on them.
Questions organisers ask
What is the difference between an assumption and a risk?
An assumption is something you treat as true today. A risk is something that may happen. Write the assumption first; if it fails, it may become a risk or an issue.
How many assumptions should the register hold?
Between eight and twenty is common for a one or two day professional event. Keep only those that would change scope, cost or date if wrong.
Who should own each assumption?
The person best placed to check it, named by role. Avoid giving every row to the secretariat.
Does this replace a risk register?
No. It feeds one. Rows that are low confidence and high impact are the first candidates for the risks you track.
Related resources
Content record: Draft. Written from the cited sources and checked by automated rules; not yet independently reviewed.