It's September, and a new member has just filled in the joining form. They're keen to get flying, and they want to know what they owe. The annual fee is on the noticeboard, but the club renews on 1 April and it's nowhere near April.
What you're after is a pro-rata membership fee: what someone joining partway through the year pays for the time left before the club's renewal date. North American clubs often call it prorated dues. There are two ways to work it out, by the day or by the month. They give different answers for the same member, so the committee has to pick one.
Here's our view. If a calculator or spreadsheet does the sum, charge by the day, because then every member pays for exactly the time they get. If the membership secretary works it out by hand, charge by the month, and accept that someone joining at the end of a month pays up to a twelfth of the fee for a few days. And whichever you choose, write it into the rules. Otherwise, sooner or later, two members get charged different amounts for the same time and the committee has nothing to point to.
The sums below are plain numbers with no currency, so they work the same in pounds, euros or dollars.
The example club#
Every example uses the same club:
- Full membership fee: 240 a year.
- The membership year runs from 1 April to 31 March. 1 April is the renewal date (some people call it the anchor date), and everyone renews on it, whatever day they joined.
The joining day counts as a day of membership, and 31 March is the last day the fee covers. A new member pays for the days, or months, from joining up to the renewal date, then renews with everyone else.
Method one: by the day#
Divide the fee by the number of days in the membership year to get a daily rate. Then multiply by the days from the joining date to the end of the year, counting the joining day.
So our September joiner signs up on 10 September 2026. The year from 1 April 2026 to 31 March 2027 has 365 days. From 1 April to 9 September is 162 days already gone, which leaves 203.
- Daily rate: 240 ÷ 365 = 0.6575
- Fee: 240 × 203 ÷ 365 = 133.48
This is the bit people get wrong. Multiply before you divide, or keep the daily rate unrounded. If you round it to 0.66 first you get 0.66 × 203 = 133.98, half a unit more than the right figure, and the error grows with the fee. Round once, at the end.
Because every day counts the same, two people who join a week apart pay different amounts, and the difference is exactly a week's membership. Nobody can say they paid for time they couldn't use. That's the main reason we like it.
The catch is the arithmetic. Counting days by hand is tedious (nobody wants to do it with a pen on the back of an envelope), and an odd figure like 133.48 is a nuisance when members pay by bank transfer. Most clubs that prorate by the day round the result, either to the nearest whole amount or up to the next one. Say which in the rules.
Method two: by the month#
Count the whole months left in the membership year, treating the joining month as a full month, and charge that many twelfths of the fee.
Our member joining on 10 September 2026 has September to March left. That's seven months.
- Monthly rate: 240 ÷ 12 = 20
- Fee: 20 × 7 = 140.00
The numbers are round, and a member can check the sum on the back of the application form. The trouble is at the edges of the month. Here's what happens to three people joining around the same time:
| Joins | Days left | By the day | Months left | By the month |
|---|---|---|---|---|
| 1 September 2026 | 212 | 139.40 | 7 | 140.00 |
| 30 September 2026 | 183 | 120.33 | 7 | 140.00 |
| 1 October 2026 | 182 | 119.67 | 6 | 120.00 |
By the month, whoever joins on 30 September pays 20 more than whoever joins a day later, for one extra day of membership. By the day the gap is 0.66. So under monthly proration, someone asking on 28 September whether to send the form now or next week would do better to wait. Some will work that out for themselves, and you can hardly blame them.
You can also do monthly proration the other way round, ignoring the joining month and counting from the first of the next one. That just flips the problem. Now someone joining on 2 September flies for most of a month for nothing. Pick one convention and write it down.
Leap years: divide by the days in the period, not by 365#
The Gregorian leap-year rule is the same in every country this guide covers. A year divisible by four is a leap year, except a century year, which is a leap year only if it's divisible by 400. So 2000 had a 29 February and 1900 didn't. The next 29 February is in 2028.
Which membership year it lands in depends on your renewal date. With a 1 January renewal, the 2028 membership year has 366 days. With a 1 April renewal, it's the year from 1 April 2027 to 31 March 2028.
Take the September joiner a year later. Someone joining on 10 September 2027 has 204 days left of a 366-day year:
- Correct: 240 × 204 ÷ 366 = 133.77
- Dividing by 365 out of habit: 240 × 204 ÷ 365 = 134.14
A difference of 0.37 is unlikely to start an argument at the AGM. But make the same mistake for a member who joins on renewal day itself, 1 April 2027, and you get 240 × 366 ÷ 365 = 240.66. That's more than the full annual fee for a full year's membership, and members will notice. A spreadsheet with a fixed 365 in the formula is right three years in four, which is exactly why the mistake can sit there unnoticed for so long. The pro-rata membership calculator counts the real days in each period, 29 February included.
Monthly proration doesn't have this problem. A month is a twelfth of the year however many days February has.
One more thing while you're choosing dates. Avoid a renewal date on the 29th, 30th or 31st of a month, and if you bill monthly, anchor on the 1st. A date that doesn't exist in every month or every year means someone has to decide what happens when it's missing, and that decision rarely gets written down.
Monthly and quarterly subscriptions#
The same two methods work inside a shorter period. Take a club charging 30 a month, renewing on the 1st, with a member joining on 20 February 2028. February 2028 has 29 days, 10 of them left, so by the day the first payment is 30 × 10 ÷ 29 = 10.34. In February 2027, with 28 days, a 20 February joiner would pay 30 × 9 ÷ 28 = 9.64.
Honestly, on monthly billing it's often simpler not to prorate at all. Start the subscription on the 1st of the following month and let the joining days go free. For small amounts that works well, as long as it's in the rules.
A quarterly subscription works the same way inside its quarter. At 60 a quarter from 1 April, a member joining on 10 May pays 60 × 52 ÷ 91 = 34.29. The pro-rata membership calculator handles monthly and quarterly periods as well as yearly ones.
Which method is fairer#
By the day is fairer, and it's the one we'd choose if your committee is happy to let a calculator or spreadsheet do the sum. Every member pays for exactly the time they get, leap years included, and nobody gains by putting off joining.
By the month is simpler. It can suit a small club where the membership secretary works from a paper form and a bank statement, and the unfairness is confined to the joining month, at most a twelfth of the fee.
While you're writing the rule, settle these too:
- Late joiners. Consider a rule that anyone joining in the last two or three months of the year pays a full year and is covered to the end of the following year. Otherwise a member joining on 15 January 2027 pays 240 × 76 ÷ 365 = 49.97 for 76 days and then the full 240 on 1 April. Rolling them on is kinder to the member, and to whoever has to chase the renewal.
- Entrance or joining fees. If the club charges a one-off entrance fee, say whether it's prorated. Normally it shouldn't be, because it pays for joining rather than for time.
- Leavers. Say whether a member who resigns mid-year gets anything back. Refunding nothing is the simplest rule. If your club does refund, use the same method in reverse.
Writing it into the club rules#
Put the rule wherever the subscription is set. In many clubs that's a set of membership regulations or committee rules that sit under the constitution or bylaws, and that the committee can change without a members' vote. Check your governing document actually says so before you rely on it. Here's wording to adapt to your own dates:
The membership year runs from 1 April to 31 March. A member joining during the year pays a proportion of the annual subscription equal to the number of days from the date of joining to 31 March inclusive, divided by the number of days in that membership year, rounded up to the next whole unit of currency. A member joining on or after 1 January pays the full annual subscription, which covers membership to 31 March of the following year. The entrance fee is not reduced. No part of the subscription is refunded on resignation.
For monthly proration, swap the calculation sentence for:
A member joining during the year pays one twelfth of the annual subscription for each calendar month remaining in the membership year, counting the month of joining as a full month.
Then publish the rule next to the fee on your joining form, so a new member can check the sum before they pay.
Prorated joining in Volanti#
Working the fee out by hand depends on the membership secretary, and it tends to go wrong when that person hands the job on. In Volanti you set up membership plans with prorated joining against your anchor date, so a new member pays the pro-rata fee when they join and renews with everyone else. Renewal reminders can go out automatically before the renewal date, and members can renew, cancel or reactivate their own membership from the pilot portal. Member management has the detail, and the page for membership secretaries shows how plans, periods and renewals fit together.
For a single joiner, or to compare both methods before the committee decides, the pro-rata membership calculator shows a yearly or quarterly fee by the day and by whole months side by side. It also prints a sheet you can attach to the member's file.