The availability and composition of preterm and post-discharge formulas (PDFs) have undergone considerable changes over the last decade. Human milk, supplemented with multi-component fortifier, is the preferred feed for very preterm infants as it has beneficial effects for both short- and long-term outcomes compared with formula. If supply of mother's milk or donor milk is inadequate, a breast milk substitute specifically designed for premature infants is the next option. Preterm formula is intended to provide nutrient intakes to match intrauterine growth and nutrient accretion rates and is enriched with energy, macronutrients, minerals, vitamins, and trace elements compared with term infant formulas. Post-natal longitudinal growth failure has been reported almost universally in extremely preterm infants. Since 2009, a nutritionally enriched PDF specifically designed for preterm infants post hospital discharge with faltering growth has been available in Australia and New Zealand. This formula is an intermediary between preterm and term formulas and contains more energy (73 kcal/100 mL), protein (1.9 g/100 mL), minerals, vitamins, and trace elements than term formulas. Although the use of a PDF is based on sound nutritional knowledge, the 2012 Cochrane Systematic Review of 10 trials comparing feeding preterm infants with PDF and term formula did not demonstrate any short- or long-term benefits. Health professionals need to make individual decisions on whether and how to use PDF.