Q:

Cannot click on input type = "radio" that is inside a HTML label?

I have a problem where I cannot click on the input type = "radio" using the id="same-supplier-no":
<label for="same-supplier-no" ng-class="{checked: !ctrl.energyModel.BillViewModel.SameSupplier}" class="">

  <input type="radio" id="same-supplier-no" name="same-supplier" ng-model="ctrl.energyModel.BillViewModel.SameSupplier" ng-value="false" ng-change="ctrl.sameSupplierValueChanged(); ctrl.analyticsProvider.sendVirtualPageView('SameSupplierNo')" class="ng-pristine ng-untouched ng-valid" value="false">

   <span></span>No

</label>

In Selenium when I do:
driver.findElement(By.id("same-supplier-no")).click();

it says that "element not visible". There are previous radio buttons in the HTML that have labels on it and they have ID's for the labels (this one does not). 
I just refer to the label id and click that instead and it works. But this one doesn't have an ID for the label and I want to avoid xpath usage, however, if I have no choice, then I will just select via xpath/css.
I have also tried via locator name i.e. By.className("same-supplier"); and using a For loop and if statement to store the input type=radio element, still doesn't work.
Question is: why can I not click the input type = "radio", why is in not visible to Selenium? Is it because it is nested inside a Label? If so, does anyone know how I can click it using the id or just getting to the element?
Thank you.
Note: I am using Java 7 for Selenium.

A:

From the chat conversation I could try some stuff on the website you are using. The radio never becomes visible. As a result of this it is impossible to use the click() method on it. 
The label that contains this radio is visible however. This means you could just use click() on this label.
driver.findElement(By.cssSelector("label[for='same-supplier-no']")).click();

Or if you really want to find the element using the radio you could use xpath.
driver.findElement(By.xpath("//*[@id='same-supplier-no']/parent::label")).click();

