If you teach at more than one gym, you will know the feeling. It is the end of the month, every gym wants an invoice, and you are scrolling back through your diary trying to remember which classes you taught where, who covered for you and which gym still has not paid for last month.
I teach group exercise across several gyms, and for a long time that was me. Each gym pays a different rate. Some want invoices by the 3rd, some by the end of the month. Cover swaps happen by text message and are forgotten a week later.
None of it is hard on its own. It just adds up, and it is easy to miss money you are owed.
This is what I do now.
1. Log every class as you go
The biggest change for me was logging each class on the day, not at the end of the month. I note the date, the gym, the class, and what kind of class it was:
- my own class
- cover I taught for someone else
- cover someone taught for me
- a cancellation, and whether the gym still paid me
It takes a minute after each class. At month end, everything is already there.
2. Keep each gym’s rate in one place
Write down each gym’s rate once: what they pay for a normal class, and what they pay for a cover class if it is different. Then you are not working it out again every month, and you can see straight away if a payment comes in short.
3. Sort out cover before you invoice
Cover is where most mistakes happen. If you taught someone else’s class, it goes on your invoice. If someone covered yours, it does not. If you swapped, keep a note of who owes whom, so the favour gets paid back.
Cancellations are worth checking too. Some gyms pay if they cancel a class at short notice and some do not. Know the rule for each gym and note it against the class.
4. Total it by gym and send each invoice
Once a month I add up the classes for each gym and send each one its own invoice. In the UK, an invoice should include:
- a unique invoice number
- your name, any business name, your address and contact details
- the gym’s name and address
- a clear description of what you are charging for, with the dates
- the date of the invoice
- the amount for each item and the total
- your bank details and when you want to be paid
The full list is on GOV.UK.
I number my invoices so I can see each gym’s history at a glance. Then I mark the classes as invoiced, so nothing gets billed twice or missed.
5. Check the money actually arrives
When payments come in, I check each gym’s total against my bank statement. This is how you spot the class that was missed off or paid at the wrong rate. A short polite email usually sorts it, but only if you notice.
6. Do not forget mileage and expenses
If you drive between gyms, keep a log of your business miles. From 6 April 2026, the HMRC rate for cars and vans is 55p a mile for the first 10,000 business miles in a tax year, then 25p a mile after that. Keep receipts for things like music licences, kit, training courses and insurance too.
This matters even more with the tax changes on the way. I wrote about that in Making Tax Digital: what fitness professionals need to know. If you are not sure what you can claim, check with HMRC or an accountant.
What I use
I did all of this in a notebook and a messy spreadsheet for years. In the end I built a proper Google Sheet that works out the pay from each gym’s rate, tracks cover and cancellations, builds an invoice for any gym and month, and keeps mileage and expenses in one place. I now sell it to other instructors through my Etsy shop, Instructor Hub. Have a look at the Instructor Pay and Invoice Tracker.
Whatever you use, the habit is the same. Log it as you go, total it once a month, and check it gets paid.
This is my journey. Yours will be unique.