If you forget to change your air filter, it can lead to a host of problems. The air filter can become clogged with dust and debris, leading to reduced air filtration and indoor air quality. This can cause health problems for you and your HVAC system. Your HVAC system will need to work harder than usual, leading to inefficiency and higher energy bills, while your family may have allergies and respiratory issues. Over time, this can cause serious health and HVAC equipment damage.