The pH, nutrient, and organic matter content should be tested and the lime, fertilizer, and organic matter additions done before planting or seeding. Low pH or nutrient levels can usually be corrected without too much added expense. Again, most soils do need some correction of pH, nutrient levels, or organic matter content. Be sure that the soil does not come from a field which has received herbicide in the past several years. Old corn fields are especially a problem.
Some herbicides have a residual life in the soil of one, two, or more years.
If they are still chemically active when you seed your new lawn or plant your garden, you may lose part or all of your planting. Ideally, the contractor will have had the soil analyzed and be willing to make a copy of the analysis available to you, though this is certainly not required by law. If the soil has not been analyzed it does not necessarily mean that it is poor quality. With some experience and knowledge of what to look for and what questions to ask, many misunderstandings can be avoided.