The limit in 2021 is $10,500. I did $10,500 but my wife did another $5000. So we over contribute by $5000. But we only reimburse $5000 from the account for now. There is still $10,500 credit in the account.
Yes, if your dependent care benefits were not rolled over or used on eligible child care expenses, TurboTax will add that $5,000 to your taxable income. After entering a W-2 with information in Box 10, TurboTax will ask if you had any funds left in your FSA at the end of the year. Whatever amount you do not roll over and is not marked for use on Form 2441 for dependent and child care expenses gets added to your taxable income on Line 1 of Form 1040. Line 1 will also say "DCB" to denote that dependent care benefits are being added to your other wages. To preview your 1040: