According to the search results, the recommended tog duvet for a 4-year-old child is between 4.5 and 7.5 tog, depending on the temperature outside and the childs personal preference. In the summer, a 4.5 tog duvet is suitable, while in the winter, a 7.5 tog duvet will keep them warm and comfortable. However, it is important to note that the temperature of the childs bedroom also plays a crucial role in choosing the right tog rating for their bedding. If the room temperature is consistently between 18°C-20°C, then a 4.5 tog duvet is suitable. If the child prefers sleeping in cooler temperatures, a 7.5 tog duvet will be perfect. It is also important to consider the childs personal preference and the temperature settings on the thermostat. If the child is like a hot water bottle, a duvet with a low tog rating will allow them to stay cool and have a well-rested sleep. On the other hand, if the child gets cold during the night, a duvet with a higher tog rating will help them stay well insulated and cosy.