Preserve relevant earlier passport, visa and admission evidence. The old details may be needed to understand prior entries and reconcile the current record.
Keep a traceable document history
Identify which passport was used for each relevant step. Do not alter historical numbers in copied records or assume an existing visa must be physically moved to a new passport; have the applicable travel requirements reviewed. Keep every page of an expiring passport on file before it is replaced, including the biographic page and any visa or entry stamps connected to prior travel.
A new passport does not carry forward the record of previous admissions, so losing access to the old document can make it harder to reconstruct entry and exit history later, particularly if an extension or a change of classification depends on that history. Scan or photocopy the full document rather than only the pages that seem relevant at the time, since a detail that looks unimportant now may matter to a later petition. Keep the old and new passport numbers linked in whatever record tracks the applicant's immigration history, and note the date each document stopped being the one presented at a port of entry.
Ask whoever prepares supporting materials whether a prior stamp or admission needs to be explained rather than assuming the new passport alone tells the full story. A consistent, traceable record avoids gaps that a reviewer would otherwise have to ask about directly.