Consolidate duplicate contacts

I need the duplicate contacts cleaned up in our account so our next campaign won't send twice to the same customer. Find and merge duplicates for anyone with the same email address, keep the record that has the most recent order and complete purchase history, and preserve their tags and subscription status. Do not change unsubscribed or cleaned statuses. After merging, export a CSV of merged IDs and the primary ID chosen and confirm there are zero exact-email duplicates left by Friday noon.

Before I push this list live, make it obvious which duplicates were risky and why. Surface the number of duplicates by recent activity: active in 90 days, active in 12 months, and dormant; show which duplicates had conflicting subscription statuses; flag any with different billing addresses or payment histories that could make a reviewer pause. Put the suggested primary contact choice at the top with the reason for that choice so procurement can approve the merges quickly.

We found three accounts for the same email during list prep: one has the latest order but missing a loyalty number, another has full purchase history but older last order, the third is unsubscribed. I am worried merging could lose loyalty points or resubscribe someone. Who should be the primary record, which fields must be preserved unchanged, and what is the safest merge order to protect unsubscribe flags and loyalty data?

Across campaigns we've lost trust and time because duplicates reappear and merges strip loyalty numbers or tags. Where are we most likely letting duplicates proliferate — import routines, signup forms, or team CSV edits — and what three habits should I change immediately to stop this: a checklist for imports, a canonical source of truth for purchases, and a daily duplicate audit?