Under RCW 26.19.080(3) (http://apps.leg.wa.gov/rcw/default.aspx?cite=26.19.080), child care expenses (along with out-of-pocket health care and long-distance transportation costs) are not included in the economic table and are supposed to be shared in the same proportion as the child support. Any payment that was made for child care expenses that were not actually incurred are to be reimbursed, in a court action if necessary--this isn't adjustment or modification (which refer to minor vs major changes, respectively), it's complying with the law.
You have the right to ask for an accounting of what was spent on daycare. Whether you can get a refund will depend on how long the child has not been in daycare; RCW 26.19.080(3) states that the right to seek reimbursement is conditioned on the amount you overpaid being more than 20% of your annual day care obligation as set forth in the order.
Many child support orders specifically provide that support is to be adjusted at regular intervals; every two years is common. Therefore, the most cost effective way to change your support order to permit you to make day care payments directly to the service provider may be when the next adjustment is made. You should review your support order and RCW 26.09.170 to figure out when it will be possible for you to seek an adjustment or modification of support.
The response does not constitute specific legal advice, which would require a full inquiry by the attorney into the complete background of the facts and circumstances surrounding this matter; rather, it is intended to be general legal information based on the limited information provided by the inquirer; it This response also does not constitute the establishment of an attorney-client relationship, which can only be established after a conflict of interest evaluation is completed, your case is accepted, and a fee agreement is signed.