I'm not sure why it's not displaying Yes/No. I've tried multiple
methods of setting the textbox value and it always works.
You're not talking about the table field being a Yes/No are you? The
textbox on the form needs to be set this way as well.

Changing the Format property of the field in table design won't change it for
any existing controls on a form bound to the field.  You'll need to change
the Format property of the Control on the form too.

If you want to show Yes or No as the value then using a combo box is a good
option. Change the control bound to the field on the form to a combo box; set
its RowSourceType property to Value List and set its RowSource property to
Yes;No.  You'll still need to set the Format property as well.

You might also consider using a check box as the control on the form; it
will be checked for TRUE (Yes) and unchecked for FALSE (No).

You can change the DisplayControl property in table design if you wish, but
as data should always be entered or viewed via forms there's not a lot of
point in doing so.

Ken Sheridan
Stafford, England