When should we say Ameen and when In sha Allah?

The hadith is as follows: …

The Prophet [salAllahu alayhi wa salam] said: “Let not any one of you say, ‘O Allaah, forgive me if You will, O Allaah, have mercy on me if You will.’ Let him be resolute in the matter, whilst knowing that no one can compel Allaah to do anything.”

[Saheeh Bukhari and Muslim]

The topic I was reading through suggested that the meaning of this is not to say inshaAllah at the end of a dua, as one should be certain that Allah swt will answer his/her prayers. In addition to this, saying inshaAllah is affirming the obvious, saying ‘Oh Allah, give me this, if you will’.

So, If you are making dua, then no, you don’t say insha’Allah, whether it is at the end of salah or in any other time. It is wrong to do so, not just unecessary. You say Ameen at end of a dua.

As for the wish. There is nothing wrong with saying “I hope to see you tomorrow, in sha’Allah” after you’ve invited someone and are expecting them to come because it is not the same as a dua.

If you plan on doing something, say in sha’Allah, just like Allah commands “Nor say of anything, ‘I shall be sure to do so and so tomorrow’ without adding, ‘Insha’Allah'” (18:23-24)

So,

I am going to the zoo tomorrow, in sha’Allah (YES)

Oh Allah, grant me righteous children, insha’Allah (NO) this is when you should say Ameen.

Allah knows best.