Can I use a letter of intent instead of a proposal?

For a marketing engagement contract?

If so, a letter of intent could be used as a starting point in the process, although I never use one. Email communication asking for a proposal is sufficient to demonstrate the fact that a potential client has asked you to prepare a proposal, this is my opinion.

Another suggestion is to bullet point what you are going to do, and then provide detail for each bullet point later on in the proposal if the client wishes to read it.

Then I take the bullet list and put it right in the statement of work clause of the contract.

Does this help you?