If you want to close a Ask.fm, you can do that easily in the Settings page.
We show below how we removed our Ask fm profile on a desktop computer:
1 Open Ask.fm
Go to http://ask.fm on a desktop computer (or click the green button below):Open Ask.fm >
2 Login to your account
by typing your associated email address and password.
can be found in the right top corner right after the login.
4 Deactivate account
is a small grey button that can be found when you scroll down to the bottom of the Settings page.
5 Click the deactivate account button
after typing your password.
Your Ask.fm profile has now been deactivated. Keep it like that and the result will be the same as a permanent removal (but that button doesn’t exist).
Source screenshots: Ask.fm