Starting with 
v201506 of the AdWords API, you can:
With these new features, you can hide old or inactive accounts to reduce clutter in your managed account's dashboard, as well as detect and exclude hidden accounts using the AdWords API.
As with the AdWords user interface, you can only hide or unhide AdWords accounts. Any attempt to hide a manager account will result in a 
ManagedCustomerServiceError.CANNOT_HIDE_OR_UNHIDE_MANAGER_ACCOUNTS error.
Don't worry -- hiding an account doesn’t affect serving:
  - You can always unhide an account by setting the isHiddenattribute of itsManagedCustomerLinkback to false.
- You can retrieve all of your accounts by setting ExcludeHiddenAccounts to false in your selector, or by not specifying a predicate on ExcludeHiddenAccounts.
- Ads in hidden accounts will continue to serve.
More manager account resources
Still have questions?  Feel free to visit us on the 
AdWords API Forum or our 
Google+ page.
 - Josh Radcliff, AdWords API Team
 - Josh Radcliff, AdWords API Team