Planning your wedding invitations well in advance is good practice to ensure all your guests are able to save the date and plan easily. A couple of months' notice is a good minimum, and you'll definitely need to start even earlier if you're planning a destination wedding. Bear in mind, however, that for some it can seem tacky to send your wedding invitations out too early.
It is recommended that you begin addressing your wedding invitations around 3 months before the wedding is due to take place. If you are using a calligrapher, contact them approximately 4 months before the wedding, just to be clear on when they require your guest list and invitation cards.
Traditionally, wedding invitations are sent out around 8 weeks before the wedding. This provides ample time to make travel arrangements and request time off work if necessary before people send their RSVP back.
Once invitations are dispatched, you need the recipients to respond in a timely manner. This will help you organise details like place cards and seating arrangements. You may want to check with your caterer when they require a final headcount to organise adequate food and drinks.
Request an RSVP date that is a minimum of 3 weeks before the wedding. As an absolute minimum, send out the invitations at least 6 weeks in advance and request an RSVP by no later than 2 weeks before the wedding. If you find yourself in a situation where some guests have not responded, don't hesitate to call them. Take a verbal RSVP or ask politely that they send a written one so you can include their details properly.
Your save the dates can include the URL for your wedding website where guests can learn more information. This is a good option that eliminates the need to send complicated invitations. Don't include registry information for gifts, as this is not traditionally a mandatory requirement of your guests.
The invitation itself can provide key information like the dress code. Try to limit this to simple attire descriptions that offer your guests all the information they need - something like "black tie" or "casual attire" will suffice. In any case, many people will tell you that your invitations can be sent out too early - ultimately, this depends on how much emphasis you place on tradition and formality.