Step up in Basis on inherited shares

Hi all – hoping you can help answer my question here.

On inherited shares sold following DOD but PRIOR to the step up in basis, are the realized gains on the sale able to retroactively reflect the stepped up basis once the process is complete at the custodian?

For context, here is a timeline for what I am asking:
1. Account holder DOD
2. Shares liquidated to split out into inherited accounts (Cost basis not stepped up yet)
3. Basis step up is finalized at custodian

At this point, would the respective 1099 at year end reflect the sale basis as is, or would it be adjusted to show stepped up basis at DOD for the realized sales?

Thank you