This TurboTax Help explains that information is required to identify your child care provider.
In Part I of Form 2441, report the names of the individuals and organizations you make payments to during the year for care provider services. The IRS also requires their addresses, Social Security or employer identification numbers, and the amount that you paid them.
The provider gives you a W-10 to tell you what name, address and tax number you should use with your tax return. If the provider did not give you a form W-10, and you do not know the provider's social security number or business tax number, you can't claim the credit until you get that number from the provider. Give them a blank W-10, ask them to fill it out with their details, and give it back to you. Keep this for your records, you do not send this to the IRS.
Form 2441 is the part of your tax return where you list your qualifying children, the details of the care provider, and the amount you paid for care, and the form calculates any credits. Even if you only had a dependent care FSA, form 2441 is used to document your eligibility to use a dependent care FSA to pay for child care.