Most, if not all, states have developed guidelines that help parties establish the appropriate amount of child support. Virginia, Maryland and the District of Columbia are no exception; each has its own child support guideline. Though the guidelines may vary from state to state, all are based at least in part on the parents' incomes and the expenses and/or needs of the children such as work-related childcare and health insurance costs. Often, the guidelines are set out in a chart-type format that calculates the child support amount as a percentage of the paying parent's income that increases with the number of children being supported and/or number of days that parent spends with the children. Many of these guidelines are also available on-line. The purpose of such guidelines is to aid the judge and parties in determining the appropriate level of support. Judges may deviate from the guidelines when there is good reason to do so. If, for example, one child has higher than average medical expenses, support for that child may be higher. Or, if the judge determines that a parent is voluntarily earning less than he or she could, the judge may impute income to that parent and calculate support using what the parent is capable of earning.