How to RSVP,
without getting it wrong.

Before you reply, find four things on the invitation: who it is addressed to, the reply date, the reply method, and what the host wants to know. The names on the envelope or the invitation are the guest list; 'and guest' means you may bring a companion, a family name means the children are included, and your name alone means just you. The date is a real deadline, because the caterer's count follows it. The method, a card, a link, a QR code, an email address, is where your reply will actually be counted, so use it rather than a different channel.

If the invitation mentions meal choice, dietary needs, a room, or several parts of the day, those are questions, and the host needs your answers to all of them.

Fill in every line: your names as the host wrote them, the number attending, the meal choice per person if asked, and a note of any dietary need. If the card has an 'M' followed by a line, it is for the title and name: 'Mr and Mrs Reid'. Post it within a few days; a card that waits on the fridge for three weeks is the reason hosts move online. If you have lost the card, a short email or message to the host with the same information is fine.

Send it to the person or address the invitation names, not to whichever of the couple you know better. Put the essentials in the first line so they survive a busy inbox: attending or not, how many, any dietary need. Add a warm sentence and stop. If the host has given a link, use the link even if you also want to send a message; the link is where the count lives.

Open the link or scan the code, and the reply page opens in your browser, usually in your own language. Say whether you are coming, how many of you there are and who they are, choose a meal if the host asks, add any dietary need, and send. You will normally get a confirmation by email; keep it, because it usually holds the link to change your answer later. Nothing to install, no account to make, no password to remember: if a reply page asks you to create an account, the host has chosen an unusual tool.

The host needs facts, not prose. One line that says who is coming and what they eat is a perfect reply. A second line of warmth is welcome.

A decline needs no reason and no apology beyond one. Reply promptly, because your seat is the one the host can give to someone else, and do not leave it vague: 'we will try' is a yes to the caterer and a no to the seating plan.

If your invitation does not say 'and guest' or name a companion, you have not been given a plus-one, and the kindest thing is not to ask. If children are not named and the invitation says adults only, the same applies. If you are unsure whether a partner is included, ask once, lightly, and accept the answer.

If you said yes and can no longer come, tell the host immediately, however awkward it feels; a late no costs nothing, a no-show costs a dinner. If you said no and can now come, ask whether there is still a seat, and take a no gracefully. If you replied online, the confirmation email usually holds a link to change the answer yourself.