Let us see what do we call a "marketing plan"? It is the result of the planning activity, a document that includes a review of the organization's place in the market, an analysis of the STEP factors as well as a SWOT analysis. A complete plan would also formulate some presumptions on why we think the past marketing strategy was successful or not. The next phase shall present the objectives we set, together with the strategies to achieve these objectives. In a logical sequence, we will further need to evaluate the results and formulate alternative plans of action. A plan would consist in details of responsibilities, costs, sales prognosis and budgeting issues.
When I ask entrepreneurs and small business owners, it is not unusual for not having any marketing plan. I once read that Sir Richard Branson never had any marketing plan when he started the 1st Virgin business many years ago. In fact in one study of entrepreneurship (I couldn't recall the name of the study) was that as much as 50% of entrepreneurs and business owners don't have a business plan and marketing plan when they first started the business.