Reuven buys a new suit but will not wear it until he has it checked for shatnez. When does he make the bracha of Shehecheyanu; when he purchases the suit, or when the begged becomes wearable after it is checked for shatnez

Shulchan Aruch Orach Chaim 223:4 writes that when someone buys new kailim, the bracha of Shehecheyanu should be said at the time of buying, even though he has yet to use them. This is because the bracha is going on the simcha that he has in buying it. Reb Akiva Eiger writes in his hagahos that if we are dealing with kailim that require tevillah in the mikva, does one say the bracha when he makes the purchase or rather after he toivels them since he cannot use it before he toivels it. The same question could apply concerning buying a new house; the owner can’t move in unless he puts up mezuzosReb Akiva Eiger stays with a tzarich iyun. This would seem to coincide with the above shatnez question. It could be that the question of shatnez is worse than Reb Akiva Eiger’s scenarios. When it comes to kailim that require tevillah; since it is something that can easily be done, one could possibly make the bracha at the time of purchase. However, in the case of shatnez, were the begged to be found to have shatnez, one would not be able to fix it but would have to return. The risk is therefore much greater and maybe one should wait to make the Shehecheyanu until after checking for Shatnez

When the mechaber discusses the bracha of Hatov U’maitiv in Shulchan Aruch Orach Chaim 222:4 he says that a person should make the bracha even if he is worried that from this good something bad will happen. It was the custom that when someone found a lost object, the king used to confiscate it. When the object is found he can make the bracha of Hatov U’maitiv, because at that point he is happy that he found a lost object. It would seem to be that at the time of buying a begged one does not worry about shatnez, therefore he can say the bracha. One may argue that the two cases are not the same. When someone finds a lost object, he is happy at that time, he just might have a future worry if the king hears about his finding. Up until the point that the king hears about it, he can use and enjoy his found object. In the case of shatnez, the begged may not be worn until he has it checked so there is no complete simcha at the time of purchase. 

The Shaarei Tzion 223:21 asks the following question on Reb Akiva Eiger based on Shulchan Aruch Orach Chaim 225:3 that says if one sees a new fruit that grows in its once-a-year season, he makes a Shehecheyanu. He should make the bracha even if he sees it on the tree or in his friend’s hand. The minhag is not to make the bracha until we actually eat it. The Gra explains the reason for making the bracha while it is in your friend’s hands is based on the halacha that when someone buys new kailim, even if they require tevillah, one makes the brachawhen it is purchased. Why does Reb Akiva Eiger have a safek whether one can make a bracha while it is in the hand of his friend? The Shaarei Tzion answers by differentiating between fruit, which is complete and ready for use even though it is in his friend’s hands, whereas kailim are not usable until they are not toiveled, and clothing is not wearable until checked for shatnez. Therefore, one should not be able to make the bracha. The Biur Halacha in 225 says that even if someone sees the new fruit on Shabbos attached to the tree and he can’t detach it until after Shabbos, he still could make the bracha as the fruit is complete. Based on this, it could be that in the case of Reb Akiva Eiger discussing a new home or a new keili that wasn’t toiveled, it is worse than a begged that needs to be checked for shatnez. He may not use a keili or live in a new home until he toivels the item or puts up mezuzos. Conversely, in the case of the begged, it is not assur since most begadim don’t have shatnez. The obligation is on the person to check the begged, but the begged is complete. This would be like seeing fruit on a tree on Shabbos

There is a differentiation between the fruit and clothing in that a fruit that grows can bring simcha to the person even if he can’t eat it. On the other hand, no one has simcha from a begged unless it can be worn. It would therefore stand to reason that Reuven does not make the Shehecheyanu until after the begged is checked for shatnez and alterations are done, so he can wear it and enjoy it! 

May we all be zocheh to say Shehecheyanu upon greeting Moshiach