How to label event marketing budget assumptions

What to take away

For an event marketing budget, this method helps you label sourced figures and illustrative assumptions. It is not a list of current agency or platform rates.

The ICO's data sharing guidance is the reference point for any cost line you build around sharing attendee data between an agency, a client and a ticketing platform.
The ASA's CAP Bitesize pages give short compliance guidance you can cite when a budget line covers promotional claims.
Eventbrite's professional services organiser page describes platform features; use its UK pricing page or a written quote to support a fee assumption.
Every figure in a cost guide should be either traceable to a named source with a date, or clearly labelled as an illustrative example.

Why sources decide whether a cost guide holds up

A cost guide earns trust when the reader can follow each number back to something published. That is the difference between a planning document and a guess.

Sourced or illustrative?

Does the figure come from a published source?

Yes

Name source and date in the same sentence

Label it as an illustrative example

The rule you apply to every figure

For a number from a published source, name the source and its date in the same sentence. If it has no source, write it as a labelled illustrative example, such as a team paying £400 a month for a platform licence.

That habit removes most of the risk in a budget document. Add the date you checked each source beside the figure, so a reader can judge how current it still is.

Where the compliance costs sit

Compliance work rarely appears as a separate invoice line, yet it drives cost. When an agency handles attendee data for a client, the ICO's data sharing request form template can help document a proposed sharing request.

The underlying legal framework is the UK GDPR and the Data Protection Act 2018. Use the ICO's Data sharing: a code of practice to scope the compliance work, not as evidence of an agency's rates.

Budget time for that work rather than treating it as free, and price it as billable time instead of an overhead absorbed into the agency fee.

The same applies to promotional claims. The ASA's CAP Bitesize short compliance guidance is a practical starting point when you check what a campaign claim can say. For a review step, cite the CAP Code, Section 3: Misleading advertising, particularly rule 3.7 on holding documentary evidence for objective claims before publication.

What the platform side of the budget looks like

Platform fees are the easiest cost to underestimate because they are usually quoted per ticket, per registration or per month. Read the platform's own description before you model it.

Labelling ticketing and registration assumptions

Eventbrite's professional services organiser information describes how corporate events are handled on the platform, including the registration flow a B2B campaign would use. That is the page to cite when you explain why a platform fee exists at all. If the platform charges per registration rather than per ticket, the cost scales with sign-ups instead of attendance.

A feature description does not establish a fee. For an Eventbrite fee assumption, check its UK pricing page or obtain a written quote, and record the fee basis and the date checked.

When a supplier quotes a retainer, project or performance structure, record which model the quote uses. Keep that agency fee assumption separate from the platform fee before you build a total.

Building the total

Put platform fees, agency time, compliance review and production in one table, then mark each line as sourced or illustrative.

Add a contingency line, say 10 per cent of the total, and label it as your own assumption, not a market rate. A reader should see which parts of the total change if a supplier changes its rate card.

A checklist for labelling budget assumptions

Name the source and date for every published figure you use.
Label every other number as an illustrative example.
Check data sharing arrangements against the ICO guidance before you price the work.
Check promotional claims against the CAP Code, Section 3, rule 3.7 before you price the review.
Confirm the platform's own description of its fees and features.
Separate one-off production costs from recurring platform and agency costs.
Record the assumptions in writing so a client can challenge them.
Review the total against the dated quotes and documented assumptions before sign-off.

Common questions

Which source should I cite for data sharing costs?

Use the ICO's data sharing guidance. It covers the arrangements between agencies, clients and platforms, and it is the reference a compliance reviewer will expect to see named.

Can I quote a platform fee without checking the platform?

No. Platform pricing and features change, so cite the platform's own organiser page rather than a remembered figure, and note the date you checked it.

For a fee assumption, use the platform's pricing information or a written quote, not a feature description alone.

How many illustrative figures is too many?

There is no fixed limit, but a cost guide where most lines are illustrative is really a template. Aim for most of your lines to carry a named source.

Does this apply outside England?

The ICO and ASA material cited here covers the whole UK. Where a rule differs in Scotland, Wales or Northern Ireland, name the nation rather than saying UK.