@Zeny Premium
With Zeny Premium, you can remove Ads, use multiple accounts, recurring entries, and cloud sync with different iPhone/iPad (auto-backup).
It is a monthly payment and you can try it for free for the first month.
@Data sync with different iOS devices
Once you subscribe to Zeny Premium, you can create your own ID to sync your data with different iPhone/iPad devices.
@Manage or cancel your subscription
If you want to cancel or manage it, Just tap the "Manage" button in the Upgrade view and tap Zeny Premium your subscription.
You can also go to the same screen from the Home screen.  
Tap Settings => Tap iTunes & App Store => Tap your Apple ID at the top of the screen => Tap View Apple ID.
When you change your devices and want to login to your Taxnote Cloud account, please tap "Taxnote Cloud" in the upgrade screen, then tap "Login" button.  You can sync to your data using your Taxnote Cloud account there.
@Restore your purchases
If you bought a Zeny Plus in the previous versions, you can restore it for free from "Restore All Purchases" button.  You can also restore your current Zeny Premium subscription with the same AppleID.