What to actually check, before, during, and after

Inventory your custom modules (which are bespoke, which are third-party, which touch core models), confirm the target version and edition in writing, take a full backup and confirm it restores, agree the downtime window early, check every third-party integration against the target version, and — if you self-host — check your Python and PostgreSQL versions against the target's requirements.

Run the migration against a staging copy of production, never against production itself. Read the full migration log rather than only the final status, time the dry run so the real cutover has a tested duration, have your team run their actual workflows on staging, track every issue in one shared list, and rehearse the rollback by restoring the backup.

When your month-end or period-close reports have run once on the new version, every scheduled and automated action has fired at least once, every integration is actually sending and receiving data, a defined hypercare window with priority response is in place, and you have a written handoff covering what changed, what to watch for and who to contact.