What is the correct syntax for referencing a row header than contains a
slash
(e.g. B/S) in a formula?

FWIW: This is a formula which is part of the criteria for a DSUM.

And Yes! I think it is related to the slashes as it works fine when I remove
them from the header and the formula.

I may not have made this as clear as I could have ...

.... this is where the row header is a means of referencing all the data in
the column, specifically:

There is a column called "B/S" with the range "Mydata" that is referenced by
the formula:

=DSUM(Mydata,"Amt",G27:G28)

where I have a calculated criteria in Cell G28, namely:

=(B/S="B")

and "B/S" is the header of one of the columns in the range "Mydata".

If I remove the slash from the formula and from the row header it works fine.

Cheers, Matt