A client emailed me this today: "This stimulus payment is not a prepayment for next year, is it?"

Someone told me it's a pre-payment on next year's taxes. Does that mean $2400 would come off what the IRS would refund for 2020 tax year?

To be clear for myself, if I was expecting a refund of $3400 for 2020 tax year, would I only receive a $1000 refund because of the $2,400 stimulus check we received?