Mustangserver 1.7.1

July 12th, 2025: We are proud to announce the immediate availability of the new version 1.7.1 of our e-invoice REST API, Mustangserver.

The release not only catches up wirh Mustangproject 2.18.0, but slightly exceeds it: one issue will only be part of the next Mustangproject release.

As mentioned in the Mustangproject announcement we now use the code already introduced in 2020 to also raise warnings in the validation of invoices which which were calculated incorrectly in a particular way. Among others, there was also a fix in the calculation of relative item allowances/charges.

With Mustangserver, you can read, write, convert and validate E-invoices. More information and the sign up for a four week evaluation period are available on the Mustangserver homepage.

2.18.0

On July 14th, 2025, we published version 2.18.0 of our cross platform open source e-invoicing toolkit “Mustangproject”.

Since November 2020 we throw exceptions when importing incorrectly calculated invoices.

Despite our request in June 2023 to add this particular check to the standard was denied, we have now added this check to our validation: we now throw a warning if quantity * price (projected on basis amount + charges – allowances, rounded to the required two decimals) of an item is incorrect.

This check is possible because we fixed am issue 887 regarding the calculation of percentual item discounts. In the import, the according Arithmeticexceptions (no longer “Arithmetricexceptions”) are now no longer catched prematurely and can be handled by the application.

Additionally: Thanks to our contributors for fixing the following:

  • support parsing of BT-90 CreditorReferenceID
  • #871 schema validation does not ignore external entities
  • #868 Fix wrong version in History.md
  • #729 Updates about SpecifiedTradeSettlementHeaderMonetarySummation and SpecifiedTradeSettlementPaymentMeans
  • #863 LineCalculator throws NPE if product is null (since 2.17.0)
  • #731 Got a broken translation key when visualizing XML into PDF (xr:Business_process_type)
  • #865 Add sevdesk signature to PDF creators
  • #849 Ignore calculation errors when extracting xml from pdf
  • #856 Read contact´s fax number.
  • #850/#843 Correction for “Re-Initialize the HTML-template on language change
  • #855 Suppress empty nodes in output XML
  • #874 Skip PDNameTreeNodes if the names are null or empty
  • #830 Invalid XML generated: Item vat-category-code summed up with other 0 percent category codes
  • #726 Financial account information (IBAN) is lost when converting a cii invoice to ubl
  • #885 JSON duplicates on item allowances/charges

Mustangproject now worth a million dollars?

The open source service provider OpenHub displays an automatic estimate how much work must have gone into the projects they list. Of course this is a very rough estimate (based on the lines of code and the basic COCOMO model) but it now states the effort that went into Mustangproject may now exceed one million dollars and with their default values may have been as much as 18 man years and $1,004,027 (on Saturday, July 5th, 2025).

The potential error margin may be quite high, but on the other hand this estimate does not include work on the website, various speeches, or contributions e.g. in the Factur-X/ZUGFeRD standardization committee.

Anyway, thanks to all contributors! And thanks for contributing this (automatic) estimate!