Knowing the amount of child support coming into your bank account is important if you're the sole or primary custodian of your child. If you're entitled to $300, you want to know that you've received all of that money, since your child's other parent should be providing some compensation to care for your child.
To determine if you've been receiving the child support you're entitled to, you need to do a little math. You are probably receiving child support checks for different amount each week, and that can be difficult to track. The Massachusetts Department of Revenue offers a calculation worksheet, or you can compare the amount you've been ordered to receive by the court by the amounts showing up via check or direct deposit.