I just want to contribute some clarification on terminology here.
Since we're filing separately and not married,
Since you are both not married to either other or anyone else, you are not in any way, form or fashion "filing separately". You are both filing single. Period.
Only one of you can claim the child in a given tax year. Period. I would recommend the one with the higher income *IF* they qualify as the custodial parent as defined by the IRS (Not as defined by a court.)
Can each of us contribute 5k (10k total) for dependent care FSA or 5k total for household?
You can. but I *highly * discourage that because one of you *will* lose on that deal. The only one that should be contributing to an FSA for the 2019 tax season, should be the one that will qualify as the custodial parent and *will* be claiming the child as a dependent on their tax return. That is the only tax filer that will see any benifit from doing this.
Now you can switch each tax year. But I recommend the higher wage earner contribute to an FSA and claim the dependent *IF* that higher wage earner qualifies as the custodial parent *as* *defined* *by* *the* *IRS*.
- Custodial parent: This is the parent with whom the child lived for *more* than 182 nights of the tax year. The nights do not have to be consecutive. Temporary absences such as hospital stays, school, night at friend's house also count, provided the child returns to the same household they were at before the temporary absence. In the case where a separation of the parents occured during the tax year, then the custodial parent is the one with whom the child lived the most nights of the year.
- Non Custodail parent: This is the parent that does not meet the criteria to qualify as the custodial parent.
