Comparing tags

 so + auxiliaire + sujet = aussi

but + sujet + auxiliaire = contraire

neither + auxiliaire + sujet = non plus

phrase affirmative  : so did I.   /  but I didn't.

phrase négative :   neither did I  /  but I did

phrase affirmative  : so did John.   /  but Robert didn't.

phrase negative :   neither did Jane  /  but Judy did

Remember - Possessive pronouns

mine

yours

his / hers

ours

theirs

The possessive tags.

Ronald's holidays were sunny, so were mine.

My holiday was great, so was his.

Our holidays were in Corsica, but John's weren't, neither were Mark's.

Examples

Kevin went to Spain but I didn't.

I ate crabs but Robert didn't.

Harry didn't play golf neither did George.

I didn't buy postcards but Jack did.