Technically speaking, there really is no difference between grant writing and proposal writing. The only difference in the two terms is found within the words themselves. Both grant writing and proposal writing offer the same outcome. Although someone writing a grant proposal may be hoping to obtain donations, the very same document could be used to obtain a bank loan for a startup business, etc., depending upon the project. This is one of the reasons that many non-profit organizations are able to obtain bridge loans from banks to cover overhead once they have received a grant award letter.
Today's standards for grant writing have been elevated to model the corporate standards for business proposal writing. For example, non-profit organizations that submit grant proposals generally have to include balance sheets, budgets and budget projections, project timelines, and even marketing plans to draw clients to their programs.
The term "grant writing" should actually be called "grant proposal writing." Grants are typically funds given based upon a proposed project, need or solution to a problem. People do not write grants. They write proposals to get the grants. Over the years, people have used the term "grant writing", perhaps without understanding that they would be required to write a proposal in order to receive a grant.
Grant proposal writing is often submitted as a response to a Request for Proposal, commonly referred to as RFP. An RFP is a document submitted by an entity with finances that is looking to pay for a solution, services, etc. The document states their guidelines and requirements for whoever would like to be awarded the money. Likewise, businesses looking for contractors may also issue an RFP.
As an instructor in both for-profit and non-profit development, I have helped people to establish their project plans so that they can be used in proposals for business as well as service development. Just as the contents of various business proposals may vary, so might the contents of various grant proposals. However, the basic structures and content of both grant writing and proposal writing are the same and may be used interchangeably.
There was a time when Foundations would only require minimal information in order to award grant dollars. However, grant making organizations such as the W. K. Kellogg Foundation, Bill Gates, The Ford Foundation and others have raised the bar for grant proposal writing. Even a growing number of smaller Foundations are requiring full blown proposals. In the past, many grantors only required short letters explaining the need for grant funding.
I still find it necessary to be mindful of what a client or student means and understands when they use the terms grant writing or proposal writing. I was once introduced as someone who writes grant proposals. The person responded, "You're just the person I need to talk to. Do you know any grant writers?"