Phosphorus is an important nutrient for cattle. Requirements have been estimated as 0.25 to 0.30% of diet DM. More recent data suggest the requirement is much lower for feedlot cattle, less than 0.15%. Grain-based diets contain a minimum of 0.25% P. Therefore, supplementation of mineral P is an unnecessary environmental and economic cost to producers. Supplementation with mineral P has been a common practice, at least historically. Other than removal of mineral P from the diet, it is unclear what other options are available to reduce P intakes. The engineering standard for nutrient excretion was one value for feedlot cattle regardless of diet. However, as more P is fed, more is excreted with intake and excretion positively correlated based on metabolism experiments (R² = 0.45). Less than 20% of P fed is retained by the animal, with the rest excreted. Recently, ASAE adopted a new engineering standard that accounts for P intake and retention to calculate excretion, which should allow for more accurate nutrient management planning. The greater challenge today is managing P inherent in common feed ingredients such as grain and byproducts. Mass balance for P was conducted using 6,366 cattle in six commercial feedlots to assess the impact of dietary P on manure P. For the average feeding period of 123 days, 4.9 kg of P was fed, 4.1 kg excreted, and 3.7 kg per animal (90.2%) removed in manure. Manure characteristics and nutrient removal were quite variable (CV > 45%). Common diets fed today vary in P concentration from 0.25 to 0.50% P depending on the amount of P-dense byproducts used. Feedlots need to distribute manure back to acres that produced grain for feeding or for processing. These byproducts are economical feeds, so managing distribution is critical for the economic and environmental sustainability of the feedlot industry.