CEDEX

[Santiago]

What is the purpose of Cedex as part of the mailing address? Should you include it? What if it has a number after it?

[DaveM]

According to my dictionary = courrier d'enterprise à distribution exceptionnelle (accelerated postal service for bulk users). In cities they may have several such boxes, hence the numbers.
So, it's probably worth quoting - depending on whether you want your letter, or your règlement, to be delivered quickly.

[Roger O]

Wiki gives it as

CEDEX
There is also a system known as CEDEX, Courrier d'Entreprise à Distribution EXceptionnelle,
designed for recipients of large volumes of mail. A postal code is allocated to each large
organisation or to post office box holders, ending in three unique digits, for example:

12 rue de Broquedis
64205 Biarritz CEDEX

CEDEX should always be written in capitals. It may be followed by a number,
if the town has more than one post office, or if it is split into arrondissements.

Ordinary deliveries would be addressed to:

12 rue de Broquedis
64200 Biarritz

It is acceptable to include a boîte postale (post office box) number as well as the
street address in CEDEX addresses.

[DaveM]

Similar to the Post Office Box system in the UK.
In my, limited, experience CEDEX applies to banks and to the CPAM, though the CPAM also supply you with a BP (Boîte Postal) address, too. Bit overkill.
Hey ho, French bureaucracy?
Like I said, how soon do you want them to cash your cheque?

[blackduff]

CEDEX is always used by Airline companies and their related companies. Since their business needs quick shipments on their mail, they always list CEDEX on their addresses.

Blackduff

[Santiago]

Similar to the Post Office Box system in the UK.
In my, limited, experience CEDEX applies to banks and to the CPAM, though the CPAM also supply you with a BP (Boîte Postal) address, too. Bit overkill.
Hey ho, French bureaucracy?
Like I said, how soon do you want them to cash your cheque?

Thanks everyone. I think I'll leave it off when I post cheques

[Roger O]

CEDEX is automatically diverted to an alternative delivery system. If the address has a CEDEX after the (special CEDEX-linked) postal code, it may end up as lost (at least temporarily). That may be OK for your cheque payment delay on the one hand - BUT if the payment date is linked to deadline overrun sanctions, it may mean you either lose what is "paid" for - or you end up paying a forfeit (as in late tax payments) which is not too productive!