The numbers you are using don't really add up. But in the example given you would owe $1,400 not $1,000 to your ex before daycare, and $1,300 to your ex after daycare.
Keep in mind that the $1,400 is your child support payment, not your income.
On the Arkansas Child Support Form work related child care expenses go on Line 8. The easiest way to figure it out is to just use the online calculator.
If you have income of $18,000 and your ex has income of $2000 (which would be 90-10) then Line 5 would be 1475 and 164. These numbers aren't set off against each other, so before daycare, your child support payment is $1475.
Work related child care expenses, child health care expenses, and extraordinary medical expenses for both parties are added up and the combined amounts are split by the relevant percentage (usually the same percentage of regular child support obligations).
Basically, in a 90-10 split your child support share is increased by 90% of your work related child support expenses and reduced by 100% of what the paying spouse pays. So, with $1000 of daycare expense, the child support goes from $1475 to $1375. So, out of $18,000 of income you'd pay $1,375 to your ex in child support and $1,000 in daycare, leaving $15,625 left over.
The Court system provides a sample calculation and order:
Sample Calculation
Step 1: The gross income of both parents is determined and combined.
Payor parent earns $2,000 and (payee parent earns $1,000, for a $3,000
combined gross income. Each parents’ share of income is then
determined based on their percentage of the combined income. Payor
earns 66.66% of the income, and payee earns 33.33% of the income.
Step 2: The basic child-support obligation is determined by looking
at the Chart for the $3,000 combined income and is $469 for the
parties’ one child. Each parent’s share of the basic child-support
obligation is then determined: 66.66% of $469 is $312.67 (payor
parent), and 33.33% of $469 is $156.33 (payee parent).
Step 3: A presumptive child-support obligation is then determined by
adding the allowed additional monthly child-rearing expenses including
health insurance premiums, extraordinary medical expenses, and
childcare expenses. In this case, the court allows $100 that payor
parent is paying for the child’s health insurance premium and $200
that payee parent is paying for childcare expenses, for a total of
$300 for additional child-rearing expenses. Each parent’s share of
additional child-rearing expenses is determining by multiplying the
percentage of income they have available for support (see step 1) by
the total expenses: 66.66% of $300 is $200 (payor parent), and 33.33%
of $300 is $100 (payee parent).
Step 4: The total child-support obligation for each parent is
determined by adding each parent’s share of the child-support
obligation with their share of allowed additional child-rearing
expenses. Payor parent ($312.67 plus $200) has a total child-support
obligation of $512.67, and payee parent ($156.33 plus $100) has a
total child-support obligation of $256.33.
Step 5: The payor receives a credit for the additional child-rearing
expenses that he is paying out of pocket. In this example, payor is
paying $100 for the child’s health insurance premium, so we deduct
$100 from payor’s total child-support obligation of $512.67. Payor
has a presumed child-support order of $412.67, which shall be rounded
down to $412.
Sample language for a court order based on the calculation provided
above:
The court has determined that Plaintiff (payor) earns a gross income
of $2,000 per month and Defendant (payee) earns a gross income of
$1,000 per month. Therefore, the parents’ combined gross income is
$3,000 with a basic child-support obligation of $469 for their one
child per the Chart. The court also finds that Plaintiff (payor) is
paying for the child’s health insurance premium in the amount of $100
per month and that Defendant (payee) is paying $200 for childcare
expenses, for a total of $300 for additional child-rearing expenses.
Plaintiff (payor) is responsible for 66% of the total obligation
($312.67 share of basic obligation plus $200 for expenses) and has a
total child-support obligation of $512.67. Defendant (payee) is
responsible for 33% of the total obligation ($156.33 share of basic
obligation plus $100 for expenses) and has a total child-support
obligation of $256.33. Plaintiff, as the payor, shall receive a $100
credit for the additional child-rearing expenses that he is paying out
of pocket. Plaintiff shall pay $412 per month to Defendant beginning
on March 1, 2020, and he shall continue to cover the child’s health
insurance premium.