What was reported in box 4 of your 2019 W-2 and what did you report for child care expenses in 2019?
In 2019, on your F2441 for child and dependent care, you would have reported $3000 in child care expenses (maximum for 1 child). If your 2019 W-2 reported $1667 in box 4 (416.67x4 months), you should have received a tax credit of for minimum 20% of the difference ($3000-$1667=$1333) or $267.
According to your scenario, you were reimbursed 100% for your expenses so in theory you were not entitled to that $267 tax credit in 2019. Therefore, due to the timing of your plan, yes you would need to include the $498 in 2020 income but you any additional tax you have incurred in 2020 has already been offset by the additional tax credit received in 2019.
