What @PattiF says if different from what I said, but it is not wrong. It's an option.
You have a choice (actually a tax loop hole). You can claim only the portion that will not be reimbursed, as I previously described. Or you can claim all your tuition on your 2021 tax return, since it will not be reimbursed until 2022 (you are technically "out-of-pocket"). But then, you have to report the reimbursement from your employer as taxable income on your 2022 tax return.
It may get a little complicated reporting the 2022 reimbursement, when you file in 2023. Reply back for instructions, if that's what you decide to do.
