This week I had to make a change to report 38 (Trial Balance By Period). I had to add a column with the balance on the end of the displayed periods. This made me realize that there is a flaw in the report if you enter a start date which will make the report not use all the columns.

For instance in a default Dynamics NAV Demo database, if you select start date 01/01/2012, you will see the report print 2 columns: 01/01/2012..31/01/2012 and 01/02/2012..31/12/9999. However, for the last column in this case, the actual net change is not calculated.
In a default demo database, you will not even notice this, because there will be no data in there for February 2012 or later.

So a simple post in the General Journal on Posting Date 01/03/2012 should give us an example. See screenshots below.

Chart of Accounts in Standard NAV:
GL Post I made:
Chart of Accounts after my post:
The actual output of Trial Balance By Period with starting date 01/01/2012:
After a bit of looking through the code, I found an easy fix for this problem.
On DataItem “G/L Account” you will find this code in the OnPreDataItem Trigger:

...
MaxCount := AccountingPeriod2.COUNT;
IF MaxCount > 13 THEN
  MaxCount := 13;

FOR i := 2 TO MaxCount DO BEGIN
  AccountingPeriod.NEXT;
...

Simple changing these lines to the following will fix the problem:

...
MaxCount := AccountingPeriod2.COUNT;
IF MaxCount >= 13 THEN //Changed Line
  MaxCount := 13
else
  MaxCount += 1; //Changed Line

FOR i := 2 TO MaxCount - 1 DO BEGIN // Changed Line
  AccountingPeriod.NEXT;
...

And behold the output of our report now:
The reason is easy enough.
They use an array to store the start/end date of each column, for the length of the MaxCount, However, they start at index 1.
The values are run through exact the same way, starting at index 2 (for i := 2 to MaxCount, meaning if 2 accounting periods to print, they only go through the loop 1 time…), and using start/end date of index-1

So if not using all columns, it is necessary to actually calculate 1 extra column for the value, but the start/end date on the last column is useless, since it is never used…