When you are bidding for a project or sending a proposal, always send a cover letter along with it. Unless of cause, you don't intend to win the project. In which case, why send it in at all?
Some experts advice that the business proposal cover letter should be a personal note from you to your main contact. I totally disagree. This line of thinking assumes that you can build a relationship with your main contact from a letter. A relationship should have been build way before you send in your proposal. If you have not build a relationship by the time you send in the proposal, chances are your competition already have and you will not win the project.
Another problem with that advice is that it assumes there is a main contact. A lot of times, especially with government contracts, there is no main contact. You have to send in your proposal and cover letter online.
Here is an example on one proposal cover letter I received via an online marketplace.
As you can see from the example above, this company tried to be personal with me and did not address my requirements. Obviously, I did not even look at their proposal much less consider them for the project.
Now, a proposal cover letter is nothing more that a sales letter. The purpose is to sell your product or services. The basics are the the same, you want to get the readers attention, get them interested, then make them desire your product or service and finally have them take action. In this case, get them to hire your business for whatever projects you were bidding for.
Now, here are some specific advice on how to write a business proposal cover letter.
I'm here to help you write better business letters.
597 Business Letters - Software