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IDProjectCategoryView StatusLast Update
0010642Talerwallet (iOS App)public2025-12-21 20:47
Reportervecirex Assigned ToChristian Grothoff Resolution deadline
ImplementerReviewer 
Release signed byDeployed by 
VerifierCommunicator 
Data protection authority notification requiredNo  
CSIRT notification requiredNo  
Estimated effort (hours)Actual effort (hours)0 
Fast-trackNo
Work packagenone
PrioritynormalSeveritytweakReproducibilityalways
Status closedResolutionno change required 
Product Version1.0 
Target Version1.3Fixed in Version1.3 
Summary0010642: When making minimum possible payment, UX questionable; and: fee seems to be charged
DescriptionThis is from a payment test on the iPhone (newest version v1.2.0 as released yesterday) and different observations can be made when trying to transfer CHF 0.00000001, the minimum possible amount an order could be created for:

- A fee is shown (there should be no fees for TOPS/CHF, as of 2025/2026 at least)
- The numbers in the UI are shown as with as footnotes markers or mathematical powers to a zero base being shown as floating no. "0.00"; it's in any case not understandable whatsoever (for normal human beings)

See screenshots attached, also to check for the sums. The final amounts I still have in my wallet seems incorrect (perhaps because of fees?)
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vecirex

2025-11-21 13:57

administrator   ~0026568

typos

vecirex

2025-11-21 14:00

administrator   ~0026570

Reposting screenshots, as I used .pdf instead of .png endings; leading to rendering issues here, even if endings should not matter in UNIX systems. :)

vecirex

2025-11-21 16:33

administrator   ~0026573

Last edited: 2025-11-21 16:36

clarify: mentioned amount is CHF (also clear from screenshots, however) and the fee charged seems to be 24,999x times that amount; and: the final sum seems to reflect the money went to the exchange, indeed

vecirex

2025-11-21 16:41

administrator   ~0026574

@stefan: Even if this gets fixed entirely, test cases to avoid this for any production system are needed to see for which ranges / at which threshold fees start to be applied, and when this happens how they apply in relation to the amount in question; maybe this also only happens under certain circumstances of the orders created, no idea.

In any case, for much higher amounts, like CHF 0.01, CHF 0.1 or even francs I never saw any fees being applied and deducted from any of my wallets.

vecirex

2025-11-21 17:02

administrator   ~0026575

clarify broken text in descr, "zero based"; extend a bit

MarcS

2025-11-22 15:08

developer   ~0026578

That's easy to explain: Fees are just the difference between raw and effective.
You want to pay less than the smallest denomination available. Then the wallet pays 1 unit of the smallest denomination, which means your payment is fulfilled and the difference is shown as fee.
==> You can never pay less than the smallest denomination.

The rendering of digits less than 1 Rappen with SuperScriptDigits is absolutely correct, see DD51 Fractional Digits.

Christian Grothoff

2025-12-07 10:23

manager   ~0026805

Marc is right.

Issue History

Date ModifiedUsernameFieldChange
2025-11-21 13:56vecirexNew Issue
2025-11-21 13:56vecirexFile Added: taler-merchant-iphone-payment-minimum-amount-app-ux.pdf
2025-11-21 13:56vecirexFile Added: taler-merchant-iphone-payment-minimum-amount-backend.pdf
2025-11-21 13:57vecirexDescription Updated
2025-11-21 13:57vecirexNote Added: 0026568
2025-11-21 13:58vecirexFile Deleted: taler-merchant-iphone-payment-minimum-amount-app-ux.pdf
2025-11-21 13:58vecirexFile Deleted: taler-merchant-iphone-payment-minimum-amount-backend.pdf
2025-11-21 14:00vecirexNote Added: 0026570
2025-11-21 14:00vecirexFile Added: taler-merchant-iphone-payment-minimum-amount-app-ux.png
2025-11-21 14:00vecirexFile Added: taler-merchant-iphone-payment-minimum-amount-backend.png
2025-11-21 16:33vecirexDescription Updated
2025-11-21 16:33vecirexNote Added: 0026573
2025-11-21 16:36vecirexNote Edited: 0026573
2025-11-21 16:41vecirexNote Added: 0026574
2025-11-21 17:02vecirexDescription Updated
2025-11-21 17:02vecirexNote Added: 0026575
2025-11-22 15:08MarcSNote Added: 0026578
2025-11-22 15:09MarcSAssigned To => vecirex
2025-11-22 15:09MarcSStatusnew => assigned
2025-12-07 10:23Christian GrothoffAssigned Tovecirex => Christian Grothoff
2025-12-07 10:23Christian GrothoffStatusassigned => informing
2025-12-07 10:23Christian GrothoffResolutionopen => no change required
2025-12-07 10:23Christian GrothoffFixed in Version => 1.3
2025-12-07 10:23Christian GrothoffNote Added: 0026805
2025-12-07 10:23Christian GrothoffProduct Version => 1.0
2025-12-07 10:23Christian GrothoffTarget Version => 1.3
2025-12-21 20:47Christian GrothoffStatusinforming => closed