A will mostly decides who has to deal with the paperwork

This works through wills and estates in the order the parts actually depend on each other.

What happens without one

Every jurisdiction has default rules determining who inherits when there is no valid will, and those rules follow legal relationships rather than intentions. Unmarried partners are excluded entirely in many systems, regardless of how long the relationship lasted. Stepchildren, friends and charities generally receive nothing under default rules.

The rules are public and can be looked up, which is a useful exercise for anyone who thinks a will is unnecessary.

The administrative function

A will names executors, who obtain the legal authority to deal with assets, pay debts and distribute what remains. Without a named executor, someone must apply for that authority under the default rules, which takes longer and can be contested.

Practically, during that period, accounts may be frozen and bills still fall due, which creates practical difficulty for a household. Naming an executor is therefore doing a favour to the people who will be dealing with it, quite apart from who inherits.

Guardianship for children

For parents of minor children, appointing guardians is frequently the most urgent reason to make a will at all. Without an appointment, courts decide, using their own criteria and without knowing your preferences. The appointment should be discussed with the proposed guardians beforehand, since they can decline.

How much weight such appointments carry varies by jurisdiction, but they are considered in most systems.

Some assets pass outside the will

Jointly owned property, certain pension death benefits and some life policies pass by their own rules rather than under a will. Nominations on pensions and policies therefore need to be kept current, and they are commonly decades out of date. An ex-partner named on an old nomination form can still receive the benefit despite a later will saying otherwise.

Reviewing nominations is a quick task that a will alone does not accomplish.

Validity is technical and unforgiving

Requirements for signing, witnessing and mental capacity are strict, and a will failing them may be invalid in whole or in part. Witnesses who are beneficiaries can invalidate their own gift in some systems. Marriage, divorce or civil partnership can revoke or alter a will automatically depending on the jurisdiction.

These are exactly the details that make professional drafting worthwhile for anything beyond the simplest estate.

The right answer depends on your tax situation, which this cannot see.

Tax is a separate question again

Inheritance, estate and gift taxes exist in some countries and not others, with wildly different thresholds, rates and exemptions. Some systems tax the estate, some tax the recipient, and cross-border estates can involve both. Reliefs for spouses, main residences, business assets and charitable gifts are common but conditional.

Practically, none of this is advice: estate and tax rules are jurisdiction-specific, change frequently, and warrant a qualified local professional.

The takeaway

Name the executors and the guardians, check the nominations on your pensions, and get the drafting done properly.

Costs compound as reliably as returns do, and in the same direction.