Maryland Worksheet B Child Support Obligation Shared Physical Custody (also known as Shared Physical Custody Worksheet B) is a form used in the state of Maryland to calculate the amount of child support each parent must pay when there is a shared physical custody arrangement. This form calculates the basic child support obligation based on the combined incomes of both parents and the number of nights the child spends in each parent’s home. The two types of Maryland Worksheet B Child Support Obligation Shared Physical Custody are “Fixed Shared Physical Custody” and “Variable Shared Physical Custody”. Fixed Shared Physical Custody is used when the child lives with each parent a set number of nights each year. Variable Shared Physical Custody is used when the child’s nights are not fixed, but vary from year to year.