Class passes, counted on your phone.

The balance is not stored. It is calculated

Balance = total − used + voided. The number itself is never kept anywhere; it is worked out from that formula every time. A stored count can drift from the records it came from, and nothing would tell you.

The ledger is append-only and holds four kinds of entry — used, added, voided, expiry extended — each with a timestamp. "Did they come last week?" has an answer you can point at.

Expiry is decided by the date, not by a record

Nothing is written when a pass expires. It is worked out from the expiry date and today, every time you look. Extend the date later and the pass is valid again, with no past record rewritten. A pass is still valid on its expiry date itself.

The use button on an expired pass is disabled and offers "extend the expiry?" instead. The extension goes into the ledger as one line.

Passes running out get a badge in both the list and the detail. The default is within 14 days of expiry, or two sessions or fewer (changeable to 7/14/30 days and 1/2/3 sessions). The badge is there whether or not you allowed notifications — notifications are never the only way to find out.

Expired passes are not shown in red. They are finished, not dangerous.

Hand over a balance summary on the spot

When a student asks how many sessions are left, you can produce a summary as text or PDF. This is free.

The app never sends anything. You choose what to share

Kartella Studio contains no networking code. There is no server, no account, no analytics SDK and no advertising SDK. Its App Privacy declaration is "Data Not Collected".

Data leaves only when you act: sharing a balance summary through the share sheet, or writing a backup to a location you pick. Those two, and nothing else.

Settings has a "where your data lives" section, so you can check the storage location and whether it is included in your device backup (you can exclude it).

Keeping student names private

The delete screen states facts only. It does not tell you what any of it means legally.

Moving to a new phone

Write a backup to a single file and read it on the new device. Reading a backup replaces everything; there is no merge (a merge would bring back students you had deliberately deleted).

The file is not encrypted and contains student names and records, so choose where you keep it accordingly. The export screen says the same thing.

The export you take immediately before deleting all data works without full access. Being left with nothing at all should not sit behind a purchase.

Free and full access

Free covers 10 active students and 3 pass templates. Recording, using, voiding, exporting a balance summary, the biometric lock, deleting, this month's totals and the expiry warning seven days ahead are all free.

Once you reach the limit, everything you already recorded keeps working exactly as before. The only thing you cannot do is add a new student.

Full access is a one-time purchase, not a subscription. It lifts the student and template limits and adds detailed reminders, all-time totals and backups. Restore purchases is always available from both the paywall and Settings.

What it does not do

There is no online booking, and passes cannot be sold inside the app — amounts are recorded, not charged.

There is no cloud sync or staff sharing. Neither fits an app that does not talk to a network. Use a backup to move between devices.

There is no student-facing app. You hand over a summary instead.

Kartella Studio is a record-keeping tool. It does not advise on how prepaid class passes are treated legally, and it does not carry out or guarantee any obligation you may have as an instructor. It makes no judgements about health, injury or pregnancy.