Conversion failed when converting the nvarchar value to data type int.

Either DMEModified.Allowed or DMEModified.Allowed has non-numeric data in it.

First try putting quotes in your where clause:

Where ProceduresFeeSchedule.FeeScheduleID = '11' (this makes the 11 a string instead of a number)

If that doesn't do it then let me know

ok, in which field is the value A4216?

DMEModified.HPCPC

then, this change should do:

update ProceduresFeeSchedule 
set ProceduresFeeSchedule.Allowed = DMEModified.Allowed 
FROM    DMEModified 
             INNER JOIN ProceduresFeeSchedule ON DMEModified.HPCPC = cast(ProceduresFeeSchedule.ProceduresId as varchar(100))
Where ProceduresFeeSchedule.FeeScheduleID = 11

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You're trying to compare an int column to a varchar column
ie.
SELECT * FROM foo WHERE IntColumn = 'abc';

The above command causes an error as the server is attempting to convert 'abc' to an integer so it can be compared to int column.

Note, this works, as '123' can be converted to an int
SELECT * FROM foo WHERE IntColumn = '123';

Basically, either
ProceduresFeeSchedule.ProceduresId is a VARCHAR column and  DMEModified.HPCPC is an INT column
or
DMEModified.Allowed is a VARCHAR column and ProceduresFeeSchedule.Allowed is an INT column

0 rows affected - should have been about 1800 rows. I am not getting the error though and thats positive news.

angel
I used your coding (snippet below). It looks like it is the cast you created, it is not linking the tables or at least not linking the fields. I get back 0 rows affected.
 

update pfs
set pfs.Allowed = m.Allowed 
FROM ProceduresFeeSchedule pfs 
JOIN DMEModified m 
  ON m.HPCPC = cast(pfs.ProceduresId as varchar(100))
Where pfs.FeeScheduleID = 11

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Your are linking a text field to a number field.  How many rows did you expect to get back?

Is their a field in ProceduresFeeSchedule that would contain 'A4216'  or is there a field in DMEModified that contains ProceduresId?

well, the error has gone :)

if the query no returns 0 row, so it is.
the problem is likely a logical problem, for example are you sure you want to join on those fields?
it could be also that really, for that join, there are no rows matching...

please double-check

OK there is no relationship between the 2 tables I found. When I put both tables in Query Designer nothing linked and i got a CROSS JOIN. Any ways around this?

can you show some sample row data from the 2 tables, and what the resulting output should be, please?