Flagging a Possibility Early
もしかしたら opens a sentence to warn that a guess is coming.
- もしかしたら雨が降るかもしれない。(It might possibly rain.)
It Wants a Partner
The sentence should end with a tentative form — かもしれない most often, sometimes でしょう or のではないか. Ending flatly leaves it dangling:
| ○ もしかしたら間違っているかもしれない | complete |
| × もしかしたら間違っている | unfinished |
This mirrors によると, which likewise opens a frame the ending must close.
The Three Forms
もしかしたら, もしかすると and もしかして all work. もしかして is the one used to open a question, and it is extremely common:
- もしかして田中さんですか。(Are you — possibly — Tanaka-san?)
That use is a politeness device: it lets you guess someone's identity without presuming.
Against もしも
もしも〜たら is a conditional — if something happens. もしかしたら is a probability — perhaps something is so. They share もし and nothing else.