When I reconcile my account qb automatically checks all my transactions. How do I stop that?

Thanks for posting a question here in the Community, @rojopax.

Normally, QuickBooks Online will prompt you whether to select all transactions or not when reconciling an account. However, the saved cache files can affect its behavior.

We can use a private browser when accessing your account to help fix this. The following are the shortcut keys you can use:

• Ctrl+ Shift + N for Google Chrome .
• Ctrl + Shift + P for Mozilla Firefox  and Microsoft Edge .
• Command + Shift + N for Safari .

Then, let's reconcile your account and check if the same thing happens.

If it works fine, clear your browser's cache to remove the stored files. Then, use a regular browser to do the task again: Clear browser cache.

However, if the problem continues, use another compatible browser instead: Supported browser.  

Also, you'll want to know how to fix common reconciliation issues in QuickBooks Online: Fix reconciliation issues.

Get back here in the Community if you have more questions about reconciliation or other QuickBooks-related concerns. I'll be here to help. Take care and stay safe always.