If your child support obligations are current, and if you have no other (potential) legal debts that could be enforced by the federal Treasury Offset Program (i.e., the mechanism that "intercepts" tax refunds to pay for certain debtor obligations), then any time is really an acceptable date to file your tax return.
There may be somewhat of a federal database lag, especially if you had a past child support debt owing, but have recently fixed that and have since become current with your payments. In that instance, you may want to wait until the next month, before filing your return, just to give some time for your debts to be reported as current.
The preferred solution, however, would probably be to contact the Treasury Offset Program itself, directly, and ask if they've updated their records accordingly. This agency may not be very forthcoming with a great deal of information, but they should be able to at least tell you that much, or if you have a current account.
Here's a link to the relevant Treasury Department webpage, which contains information on how to reach them:
https://fiscal.treasury.gov/fsservices/gov/debtColl/dms/top/debt_top.htm
Thanks for asking this important question.
