This thesis investigates of the compliance cost of the current and possible future configurations of the nutrient management regulations on Ontario dairy farms. Three optimization models representing small, medium, and large Ontario dairy farms were solved under regulatory scenarios simulating variations of the current Nutrient Management Act (NMA) and the proposed Clean Water Act (CWA). Under the NMA regulations, small, medium, and large Ontario dairy farms do not incur compliance costs. Under stricter NMA regulations, large farms may face compliance cost up to 24% of net return. Dairy farms with low soil P will not be able to comply with these stricter regulations. Medium and large dairy farms will incur higher compliance costs under the proposed CWA regulations. Manure export and land rental can reduce compliance costs for the CWA regulations. If regulations in the CWA were made stricter, medium and large farms will see an increase in compliance costs.