Generally you will want to keep an records related to the distributions and any repayments you have made.
Did you receive an RMD from an IRA in 2020? Did you return some or all of it within 60 days of each RMD distribution? For money that you returned after 60 days, was any of that money returned prior to August 31, 2020?
I'm not sure, but you may receive a Form 5498 in May showing the repayments as a rollover, which is how they are being treated by the IRS.