Error 266 - I'm Confused, Only One Transaction With COMMIT And ROLLBACK

I have a transaction that calls one other sproc and also executes another set of queries, but for some reason I'm getting error 266: "Msg 266, Level 16, State 2, Procedure AddUserHaveTag, Line 26.  Transaction count after EXECUTE indicates that a COMMIT or ROLLBACK TRANSACTION statement is missing.  Previous count = 0, current count = 1."
There is NO transaction in the sproc AddTag.  It is also included below.

Here is the sproc with the transaction:1 set ANSI_NULLS ON
2 set QUOTED_IDENTIFIER ON
3 go
4
5 ALTER PROCEDURE [dbo].[AddUserHaveTag]
6 (
7 @UserHaveID int,
8 @Tag varchar(24),
9 @UserHaveTagExists bit OUTPUT
10 )
11 AS
12 SET NOCOUNT OFF
13 DECLARE @ErrorCode int
14 DECLARE @TagID int
15 DECLARE @TagExists bit
16
17 BEGIN TRAN
18
19 -- Call proc to add tag to Tags table
20 EXEC AddTag @Tag, @TagID OUTPUT, @TagExists OUTPUT
21
22 -- Check for errors
23 IF @ErrorCode <> 0 GOTO ERROR
24
25 -- Check for existing record, otherwise insert
26 IF EXISTS (SELECT 1 FROM UserHaveTags WHERE UserHaveID = @UserHaveID AND TagID = @TagID)
27 BEGIN
28 SET @UserHaveTagExists = 1
29 RETURN 0
30 END
31 ELSE
32 BEGIN
33 INSERT INTO UserHaveTags (UserHaveID, TagID) VALUES (@UserHaveID, @TagID)
34 SET @UserHaveTagExists = 0
35 END
36
37 -- Check for errors
38 IF @ErrorCode <> 0 GOTO ERROR
39
40 COMMIT TRAN
41
42 ERROR:
43 IF (@ErrorCode <> 0)
44 BEGIN
45 PRINT 'Unexpected error occurred!'
46 ROLLBACK TRAN
47 END
  Here is the AddTag sproc:1 set ANSI_NULLS ON
2 set QUOTED_IDENTIFIER ON
3 go
4
5 ALTER PROCEDURE [dbo].[AddTag]
6 (
7 @Tag varchar(24),
8 @TagID int OUTPUT,
9 @TagExists bit OUTPUT
10 )
11 AS
12 SET NOCOUNT OFF
13
14 IF EXISTS (SELECT 1 FROM Tags WHERE Tag = @Tag)
15 BEGIN
16 SELECT @TagID = TagID FROM Tags WHERE Tag = @Tag
17 SET @TagExists = 1
18 RETURN 0
19 END
20 ELSE
21 BEGIN
22 INSERT INTO Tags (Tag) VALUES (@Tag)
23 SET @TagID = SCOPE_IDENTITY()
24 SET @TagExists = 0
25 ENDAny advice?Also if you see any glaring errors or things I could be doing better, I'm open to suggestions. I'm fairly new to sprocs and transactions. Thanks,
Travis