First double check your spelling.
Second double check the syntax for your subform reference.  See :
Value From a Form
Value From Subform

Let's see the code.

I have used these check boxes and they work great. Any help would be appreciated.

In the AfterUpdate event for these three check boxes I have:

Private Sub TriageComplete_AfterUpdate()

     FormatToggleButtons ([Name])

End Sub

I have also tried FormatToggleButtons ("TicketDetailF") which is the name of the parent form and I do not get the error any longer but the check boxes do not change value when clicked.

Since they are located on a subform I have also tried FormatToggleButtons ("Forms!TicketDetailF!PotentialIssueF") and get the not found error as well.

Name of the parent form is TicketDetailF
Name of the subform is PotentialIssueF and that is also the name of the control.

I have used your function located in its own module:

Public Function FormatToggleButtons(FormName As String)

    Dim C As Control
    
    For Each C In Forms(FormName).Controls
        If C.ControlType = acToggleButton Then
            If C.Value Then
                C.Caption = "P"
            Else
                C.Caption = ""
            End If
        End If
    Next

End Function

I set up a Public variable in the module:

Public ParentForm As String

I initialised this variable in the Load event of the Parent form:

ParentForm = Me.Name

I then edited the first line of For Each loop:

For Each C In Forms(ParentForm)(FormName).Form.Controls

I must be missing something Kevin. Here is my module with the added lines of code you suggested. I also added ParentForm = Me.Name to the parent form's On load event.

Option Compare Database
Option Explicit
Public ParentForm As String

Public Function FormatToggleButtons(FormName As String)
    Dim C As Control
    
    'For Each C In Forms(FormName).Controls
    For Each C In Forms(ParentForm)(FormName).Form.Controls
        If C.ControlType = acToggleButton Then
            If C.Value Then
                C.Caption = "P"
            Else
                C.Caption = ""
            End If
        End If
    Next

End Function

Which line is causing that error? It's easier if we can see it in the debugger.

Ok. I found the problem. I forgot about the code in the OnCurrent event. I had it remmed out for testing.

Instead of initialising the ParentForm variable in the Load event of the parent form add the code before calling the function in the OnCurrent event of the Subform.

Private Sub Form_Current()

    ParentForm = "ParentFormName"
    FormatToggleButtons ("SubformName")
    
End Sub

The reason for the error was the function was being called BEFORE the value was set in the variable.
Event timing can be weird sometimes.

I'm still getting the error. The line of code that seems to be causing the error is

For Each C In Forms(ParentForm)(FormName).Form.Controls

Located in the module.

I'm sorry Kevin and Richard. I imagine this is frustrating for you as well. I'm trying only give you what you needs instead of just dumping a bunch of code here.

I've used these check boxes on other forms and they have worked perfectly. Add a subform into the mix and it all fell apart on me.