I have claimed my dependent for the last two years. We don't have a formal custody agreement, but he generally has her at least 1/3 of the time, so I believe we're considered joint custodians.
This upcoming year, we decided he will claim the dependent. Will I be able to claim anything that relates, such as childcare costs? Should I file as Head of Household or Single in 2023?
There is no such thing as joint custody for the IRS. For the IRS, the custodial parent is the one with whom the child spent the most nights----at least 183 nights
Are you the custodial parent? Do you have an agreement with the other parent to allow the other parent to claim them--due to divorce or that you live apart and share custody? Did one of you sign a Form 8332?
If there is a signed 8332 then the custodial parent retains the right to file as Head of Household, get earned income credit and the childcare credit. The non-custodial parent gets the child tax credit for children under the age of 18.
As far as the IRS is concerned, the custodial parent is the one with whom the child spent the most nights during the tax year--at least 183 nights.
If you are a non-married couple who live together then only one of you can claim the child(ren) and the one not claiming the child does not enter anything at all on their tax return about the child.