by lostphd
I found it. It's on page 12 of the GERMAN rules, just above the credits. Loosely translated, it says:"In the loan payment phase, players pay an additional franc interest if they have 2/3/4/5 or more loans in the 2/3/4/5 person game."
It is listed as an optional rule.
See the link here:
http://lookout-spiele.de/wp-content/uploads/LeHavre_Regeln_2...
The rule obviously is not intended to apply to Australian speakers :)