I want to open a custodial Roth IRA for my 17 year old granddaughter who had earned income for 2020. I know I have until the time she files her tax return to contribute but must I open the custodial Roth IRA account before December 31st of 2020 (even if I do not make the contribution until I know what her earned income is when she gets her W-2?

I cannot find any information and don’t want to lose the opportunity to open the account if it needs to be done before the end of Dec. 2020.