It depends. Under RCW 26.26B.040, the court has the discretion to order back child support from the time the child was born to the issuance of the final orders. This period is limited to 5 years. However, there are many factors that go into awarding back child support. If the State of Washington has paid certain public assistance to the birth mother, it may be entitled to a portion or all of the back support for periods when the public support was paid. In those circumstances, the State of Washington through the Prosecuting Attorney’s Office may request the back-child support, which will be due to the State if awarded. If there is no public assistance, the custodial parent may request back support as a part of the paternity action.