A judgment was entered by default as I did not file a response to the action and the other parent and I agreed at the time. Can I modify the default judgment?

Yes, a parent may modify a default judgment regardless of whether they filed a response or otherwise participated in the case. The same rules of a substantial change of circumstances is required. However, if no response was filed, that parent will be required to pay the 1st appearance filing fee in addition to the filing fee to modify their order. As if the date of this blog, the 1st appearance fee is currently $435 and the filing fee to modify a custody order is $115. Keep these fees in mind if you find yourself in this situation.