The adjectives erforderlich and förderlich appear and sound very similar, but have very different meanings. I have found myself constantly having to check these words in a dictionary when writing business emails in German, so writing this lesson is hopefully going to help me learn the differences between the two as well!

The first of the two adjectives, erforderlich, is usually used to reinforce the serious necessity of a statement, and can be translated variously as "necessary," "required," "essential," "requisite," "needed," and "consequential."

BANNER PLACEHOLDER

Die Partner sollten dieses Angebot annehmen und die Chance nutzen,

The partners should accept this offer and use the opportunity,

denn es ist dringend erforderlich.

as it is urgently necessary.

Captions 63-64, Angela Merkel - Gemeinsame Pressekonferenz mit Barack Obama

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Nur bei einem Notruf erfolgt eine Datenübermittlung,

Only in the case of an emergency call is a transfer of data carried out

und dann werden auch nur die Daten übermittelt,

and then also only the data are transferred

die für die Erbringung der Hilfeleistung unbedingt erforderlich sind.

that are absolutely essential for the provision of assistance after the accident.

Captions 36-38, Sicherheit im Straßenverkehr - Versicherer entwickeln automatischen Notruf für alle Autos

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As you may have noticed, the texts above are respectively from a government official and a statistician, and thus the sentences are quite complicated. In fact, both erforderlich and förderlich are more often used in written German and far less in spoken German. Here are some examples of förderlich from written German sources: 

Dabei konnte ich ihm zu meiner großen Freude förderlich sein.
To my great joy I could be of use to him in that matter.
From Heinrich Mann's novel Der Untertan, in the 1921 translation by Ernest Boyd under the title "The Patrioteer."

Wenn die Boote gleich reihenweise ausfallen, ist das nicht gerade förderlich.
It's not exactly beneficial if the boats drop out in rows. 
From a 2006 article in the newspaper Die Welt. 

Jedenfalls reicht aber die Stabilität so weit, dass sie genügt, ein förderliches Ideal einer Wissenschaft zu begründen.
In any case, however, the stability extends so far that it is sufficient to establish a beneficial ideal of science.
From Ernst Mach's article "Erkenntnis und Irrtum" in Philosophie von Platon bis Nietzsche, Berlin 1905.

The adjective förderlich can be variously translated as "beneficial," "of use," "advantageous," and "conducive."

It's easiest for me to remember the difference between the two in that erforderlich is usually associated with a demanding tone and thus more serious, so I remember: the longer word is more serious. On the other hand, förderlich is usually used in a positive and thus lighter context, so  I remember: the less serious word is the shorter of the two.

Further Learning
Write some sample sentences in English mixing the various translations of the two words above, then test your knowledge by translating the sentences into German and see if you translated erforderlich and förderlich correctly.