When you pepper your bids, proposals and other client communications with your own in-house jargon, you demonstrate your inward, internal, self-focused thinking.

You give him or her the clear message that you are either unable or unwilling to think or communicate from any perspective other than your own / your company’s.

And you indicate to them that they’ll have to constantly make the effort to interpret you and your position, rather than vice versa, as it should in fact be. 

To prevent this internal speak and in-house or industry jargon, pair up with someone who can competently and knowledgeably role-play a representative from the customer / client organisation (i.e. someone who KNOWS the customer organisation’s relevant personnel).
 
Read the copy aloud to that person and have them stop you as soon as they hear a word, term or phrase with which they are unfamiliar, or that smacks of your company’s internal processes and philosophies.

Better still, read the copy aloud to several people role-playing a variety of the client’s key personnel. That way, you’ll also pick up on language that may be too technical for some.