Can I switch tax off for a while without deleting my rates?

Yes. Go to Settings → Store Settings → Manage Tax:

1. Click Tax Settings.
2. Untick Enable tax on this store.
3. Click Save Settings.

Checkout stops adding tax straight away, and all your rates stay in the list. A yellow box confirms Tax is turned off for this store and says how many rates won't apply.

When you are ready, click Enable tax in that box, or tick the setting again. Your rates apply again with no need to re-enter them.