Here is the part nobody tells you about until you're in it.
Death certificates. You will need more of these than you think. The funeral home will file for them, but you need to order enough copies. Typically 10 to 15. Each financial institution, government agency, and insurance company will want an original certified copy. They will not accept photocopies. They will not accept digital scans. They want the paper with the raised seal.
Banks, investment accounts, retirement accounts, life insurance policies, vehicle titles, real estate deeds, pension plans, Social Security. Each one requires its own certified copy. Order more than you think you need. They cost about $10–$25 each, and it is far easier to order extras upfront than to wait weeks for additional copies later.
Social Security. You must notify the Social Security Administration of the death. The funeral home typically does this, but confirm. If the deceased was receiving Social Security benefits, payments stop the month of death. Any payment received for the month of death must be returned. If you are a surviving spouse or dependent, you may be eligible for survivor benefits. The full picture of Social Security survivor benefits is more complex and more valuable than most families realize.
Employer and pension. If your person was still working, notify their employer. If they had a pension, notify the pension administrator. If they had a 401(k) or IRA, contact the financial institution. Beneficiary designations on these accounts supersede the will, so the money goes directly to whoever is named, regardless of what the will says.
Life insurance. Locate all life insurance policies. Call each company to initiate the claims process. You will need a death certificate for each claim. The full picture of what happens to life insurance when someone dies, including beneficiary rules and payout timelines, is worth reading before you call.