What should you write when you accept or decline a written invitation? The phrases you use depend on the formality of the invitation.
Sample phrases to use in an informal invitation
"Please come to our party on..."
"Would you like to come to dinner on...""
"Can you make a meeting at 3pm..."
To accept an invitation to an informal party / dinner, you can write:
"Thanks for your invitation / invite. I'd love to come."
"Thank you for inviting me to dinner. I'm looking forward to it very much."
(For a meeting)
"I'm able / free to come to / attend / make the meeting at..."
To decline these invitations, you can write:
"Thank you for your invitation, but I'm sorry I can't come."
"I'm sorry, but I'm not going to be able to make it on..."
Writing invitations samples
"We would be delighted if you could attend the opening ceremony of..."
"Mr and Mrs Jones request the pleasure of (name's) company to celebrate the wedding of their daughter Rebecca."
To accept a formal invitation:
"Thank you for your invitation to the opening ceremony. I would be delighted to attend."
Thank you for your invitation to Rebecca's wedding. I would be delighted to attend."
To decline a formal invitation
"Thank you for your invitation. However, I regret that I will be unable to attend."
"Thank you for your invitation to.... Unfortunately, due to a prior commitment, I will not be able to attend.
If you are declining a formal invitation, it's customary to say why you can't attend with a phrase such as "Due to a prior commitment, I will not be able to attend..."
With formal invitations (but not wedding invitations) you can also end your letter / email with a phrase such as "Wishing you every success with the (name of event)."