Hi,
this message is trying to tell you that Access can't find one of the fields
you have in your code.
Here are the fields/controls used in your code:
[Curr Tax Yr]
ID
subfrm: 1040 Appointments

you can use Debug.Print to check for missing fields
add the following 3 lines of code immediately after the line
'Opens the edit add/edit client appointment time and date

Private Sub EditAppt_Click()
'Opens the edit add/edit client appointment time and date
   Debug.Print "[subfrm:1040 Appointments]: " & [subfrm:1040 Appointments]
   Debug.Print "Curr Tax Yr: " & [subfrm:1040 Appointments].Form![Curr Tax
Yr]
   Debug.Print "ID: " & ID
save the form, open in normal view and run the form
press Ctl + G to open the immediate window and see what Access has put for
subfrm:1040 Appointments, Curr Tax Yr, ID
any that have a blank after the colon are the ones that Access can't find
When Access can't find a field it gives the message can't find field "|"
where it is using "|" to represent the name of the thing it can't find.

Often there is an error finding controls on a subform
A subform is inside a subform control similar to the way a picture is inside
an image control.
The name of the subform control is often different from the name of the
subform.
To get the name of a control on a subform you need to go
Me.[subform control name].Form.[control name]

you should replace
[TaxYear] = " & [subfrm: 1040 Appointments].Form![Curr
Tax Yr]

with
[TaxYear] = " &Me. [name of subform control].Form![Curr
Tax Yr]

and
"[CltID] = " & [ID]

with
"[CltID] = " & Me!ID

Jeanette Cunningham