Your society knows this person. Your registration form does not.

The most expensive delegate at your congress is the member who registered as a non-member. They paid more than they owed, you now owe them a refund or an argument, and somewhere in your records there are two versions of the same person. None of this is their fault. It is what happens when membership and congress registration run as two operations that happen to share a logo.

Most congresses are small enough for this to hurt

ICCA recorded 12,438 international and regional association meetings in 2025 [1]. Very few of them are the multi-thousand-delegate congresses that make the trade press. Meetings with 50 to 249 participants made up 60.4 per cent of the total, and nine out of ten meetings had fewer than 1,000 participants [2][3]. That is the scale at which the registration list is a spreadsheet, the finance office is a volunteer treasurer, and nobody has time to cross-check 180 delegates against the membership database by hand. It is also the scale at which the gap between the member and non-member rate is a meaningful share of the budget.

What the large societies write into their terms

Look at how societies with professional staff handle this, because their registration pages are a record of the problems they have already had. The Society for Neuroscience charges an advance in-person rate of US$690 for members and US$1,245 for non-members at Neuroscience 2026, and its terms state that “membership must be current and in good standing at the time of registering” [4]. It goes further: “Refunds will not be issued for incorrect registration categories”, and if you register in the wrong category before your status is verified, “the difference will not be refunded to you as membership is not retroactive” [4].

The American Geriatrics Society sets a US$825 member and US$1,195 non-member physician rate for its 2026 annual meeting and requires that “your membership must be valid through the 2026 Annual Meeting dates” [5]. INFORMS prices its 2026 annual meeting at US$750 for members and US$1,080 for non-members, requires membership to be active “at the time of the meeting”, and folds a year of membership into the non-member fee [6]. The European Society of Cardiology’s 2026 congress lists an early fee of €995 for non-members against €845 for professional members [7].

Four societies, at least three different answers to when membership must be valid, and one shared assumption: that the registration system can actually tell who is a member. These are examples of published terms, not a survey, and your society can borrow the wording. What it cannot borrow is the staff who enforce it.

Where the stranger comes from

In our experience the member who arrives at registration as a stranger is rarely trying to. The usual routes are dull. Their membership is registered under a previous institutional email address and the registration form treats the new one as a new person. They renewed by bank transfer in February and the treasurer has not yet marked it paid. Their membership lapsed three weeks before the congress and nobody, including them, knows whether your grace period covers it. They are a doctoral student whose card says student but whose registration form has no way to prove it. A colleague or a departmental administrator registers on their behalf, with the administrator’s details. Or a professional congress organiser runs registration in its own system, and your membership list reached it as an export taken in March.

Each of these is a small, sensible thing. Together they produce the email the treasurer dreads in the week after early-bird closes: forty people who paid the non-member rate, a list of names that half-match the membership database, and a committee asking why the registration income is above budget and the membership income below it.

The reconciliation bill

Correcting it costs more than the difference. If you refund the overpayment by card, the payment processor keeps its cut. Stripe’s own documentation is plain: “Stripe’s processing fees from the original transaction aren’t returned” when a payment is refunded, in full or in part [8][9]. The delegate then sees the credit “approximately 5-10 business days later” [8], which is a second email, from the same person, asking where it is. Other providers publish their own terms and they differ, so read yours before you promise anyone a clean refund.

Then there is the time. Every mismatched record is a volunteer looking up two systems, deciding which is right, and writing to a member to explain a decision that should never have needed making. Count those hours honestly and the member rate stops looking like a discount and starts looking like the cheaper way to run the event.

Two records for one person is a compliance problem too

The duplicate record is not just untidy. In the UK, the UK GDPR requires personal data to be “accurate and, where necessary, kept up to date” and says every reasonable step must be taken to correct or erase inaccurate data without delay [10]. The Information Commissioner’s Office puts the duty in practical terms: take all reasonable steps to ensure the data you hold is not “incorrect or misleading as to any matter of fact” [11]. The EU GDPR carries the same accuracy principle in the same words [12].

A membership record that says lapsed and a delegate record that says member, for the same human being, is a fact your society is getting wrong about that person. That is the UK and EU position; societies with members elsewhere are working to other regimes as well, and this post does not describe them. The point stands in any jurisdiction: one person, one record is a governance standard, not a tidiness preference.

Before your next committee meeting

Most of the fix is decisions, not software, and the decisions belong to the committee.

• Decide when membership has to be valid. At the moment of registration, or through the congress dates? The societies above chose differently. Either works. Not choosing is what fails, because then the treasurer decides case by case in December.
• Write the refund rule down before registration opens. If you will not refund the difference for a wrong category, say so on the form, as the Society for Neuroscience does [4]. If you will, decide who approves it and where the processing fee comes from.
• Put join and renew inside the registration journey. A non-member who can become a member in the same transaction has no reason to register as a stranger. A lapsed member who sees their own record has no reason to create a second one.
• Identify people by login, not by email address. Email addresses change every time someone moves institution, which in academia is often. The record should survive that.
• Reconcile when early-bird closes, not when the congress does. The mismatches are cheapest to fix while the delegate still has a reason to reply.
• If a congress organiser runs registration, agree how membership status reaches them live, and who owns the delegate data afterwards. An export taken in March is wrong by June.

This is the same discipline we described for certificates of attendance: the data you need at the end of a congress is either captured cleanly at the start or reconstructed expensively afterwards.

Membersites recognises an existing member at congress registration and applies the member, non-member or student rate automatically, because the membership site and each conference site share one login and one member record.

If your treasurer has spent a week matching names against a delegate list, we are happy to talk through how yours could work instead.

References

1. ICCA. ICCA Releases ICCA GlobeWatch: Business Analytics – Country & City Rankings 2025 at IMEX Frankfurt. International Congress and Convention Association, 19 May 2026. https://www.iccaworld.org/news/post/icca-releases-icca-globewatch-business-analytics-country-city-rankings-2025-at-imex-frankfurt/. Accessed 28 September 2026.
2. ICCA. GlobeWatch Business Analytics: 2025 Country & City Rankings – Public Abstract. International Congress and Convention Association, 2026. https://iccaworld.aflip.in/40e7879607.html. Accessed 28 September 2026.
3. TTG Associations. Association meetings frequency, economic value on the rise: ICCA study. TTG Asia Media, 20 May 2026. https://www.ttgassociations.com/2026/05/20/association-meetings-frequency-economic-value-on-the-rise-icca-study/. Accessed 28 September 2026.
4. Society for Neuroscience. Neuroscience 2026 Registration Fees. SfN, n.d. https://www.sfn.org/meetings/neuroscience-2026/registration/registration-fees. Accessed 28 September 2026.
5. American Geriatrics Society. AGS26 Annual Meeting Registration. AGS, n.d. https://meeting.americangeriatrics.org/registration. Accessed 28 September 2026.
6. INFORMS. Register – 2026 INFORMS Annual Meeting. Institute for Operations Research and the Management Sciences, n.d. https://meetings.informs.org/wordpress/annual/register/. Accessed 28 September 2026.
7. European Society of Cardiology. ESC Congress 2026 Registration. ESC, n.d. https://www.escardio.org/Congresses-Events/ESC-Congress/Registration. Accessed 28 September 2026.
8. Stripe. Refund and cancel payments. Stripe Documentation, n.d. https://docs.stripe.com/refunds. Accessed 28 September 2026.
9. Wise. Stripe fees: a complete guide to processing fees and other costs. Wise, updated 18 May 2026. https://wise.com/us/blog/stripe-fees. Accessed 28 September 2026.
10. UK Government. Regulation (EU) 2016/679 (United Kingdom General Data Protection Regulation), Article 5. legislation.gov.uk, n.d. https://www.legislation.gov.uk/eur/2016/679/article/5. Accessed 28 September 2026.
11. Information Commissioner’s Office. Principle (d): Accuracy. ICO, n.d. https://ico.org.uk/for-organisations/uk-gdpr-guidance-and-resources/data-protection-principles/a-guide-to-the-data-protection-principles/accuracy/. Accessed 28 September 2026.
12. European Union. Regulation (EU) 2016/679 (General Data Protection Regulation), Article 5. EUR-Lex, 27 April 2016. https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32016R0679. Accessed 28 September 2026.