What to write in a letter to your child.

To a baby or toddler

They'll have no memory of any of this, which makes you the only surviving witness. Write like one.

• The day they arrived: the hour, the weather, who cried.
• How you chose the name, and what you nearly called them instead.
• What they're like at this exact age — the noises, the obsessions, the refusals.
• What being their parent has been like so far, honestly.
• What you were like before them.

You are eleven months old and terrified of the vacuum.

To a child between five and twelve

This is the age with the best material and the shortest shelf life. Write down the way they talk before it changes.

• Something they said that you've repeated to other adults.
• Their current best friend, and why.
• What they want to be, in their own words.
• A day out that mattered more to you than to them.
• What you admire about them that has nothing to do with school.

To a teenager, or for eighteen

The eighteenth-birthday letter is the one most parents want to write and most put off. Write it early — the feeling is strongest while they're still small.

• What you were doing at eighteen, including the mistakes.
• What you hope they don't apologise for.
• How to know when to leave a situation.
• The thing about your own parents you've never told them.
• That the door doesn't close — say it plainly.

To a son, to a daughter

Don't write a letter to a category. The useful version isn't "advice for my son" or "advice for my daughter" — it's what you have specifically noticed about this specific person.

If a sentence would work in a letter to someone else's child, cut it.

What to leave out

• Expectations disguised as encouragement.
• Anything that scores a point in an argument you're currently having.
• Grievances about the other parent.
• Promises about the future you can't control.

When it should arrive

Match the letter to a moment: a birthday, the end of school, a first home, a wedding, the birth of their own child.

Write several, date them, and let each one open when it's needed. You don't have to decide the whole sequence today — one letter is already more than most children ever receive.