Many mitzvahs require a bracha beforehand. If one were to not make the bracha, is the mitzvah valid bedi’eved or does the fact that the bracha wasn’t made means the mitzvah wasn’t done?
If you put on a tallis but didn’t made the bracha, does it count as wearing a tallis?
If you washed before bread but didn’t make an Al Netilas Yadayim, does it count as washing?
If you searched for chametz in the correct time but didn’t make the Bracha, does it count as a valid bedika?
I think the point is clear after all those examples 😁
Ps: these halachos (https://outorah.org/p/32929/) seem to say the rule about whether you can still make the Bracha, but it doesn’t say whether or not you were mikayim the mitzvah after the fact.