Is it possible to restart the whole bookkeeping for last 3 years?

Good morning, finance-ghvimmig.

Thanks for joining us here in the Community. I'd be happy to provide some information.

Since your account is older than 60 days, the option to completely start over isn't available. To start fresh, you'd have to cancel your subscription, then start a new one. Let me show you how. 

Cancel your subscription:

1. Sign in to your QuickBooks account.
2. Head to the "Gear" icon and select "Billing and subscription"
3. Find the product you wish to cancel, then select "Cancel."
4. A multiple choice survey will pop-up on why you're cancelling your subscription. Once you’ve filled it out, select "Continue to cancel."
5. You’ll see a page that details product benefits, and the last day you'll be able to use your subscription. Select "Continue to cancel."
6. You should now see a second pop-up confirming your subscription is cancelled. Select "Got it".

Here's a guide for reference. 

Note: This guide also provides the steps to cancel an account that was purchased from Apple or Google play store

To start a new account:

Visit the QuickBooks homepage and sign up for a new account. You can use the same user ID and password that you did previously.

1. Sign up for QuickBooks Online.
2. Enter your user ID and password. You can use the same user ID and password as before, keeping in mind that the account you've just cancelled will still show in the list of companies for the next 12 months. You can also chose to use a different email address.

I hope this helps!

If you have any other questions, feel free to reach back out.