You are taking the same day as in your original date, and if this is
31 then there is no date 31st February 2005 - in this case, Excel will
wrap the number around and make it 3rd March 2005, and thereafter it
will be the 3rd of each month - adjust your formatting to dd/mm/yy to
see.

You might like to change your formula to:

=DATE(YEAR(B5), MONTH(B5)+1, 1)

so you will always get the 1st day of the next month.

Hope this helps.

Pete

On Nov 21, 7:28 pm, Dermot wrote:
I create this formula and copied it down.

=DATE(YEAR(B5), MONTH(B5)+1, DAY(B5))

I have custom formatted the date: mm/yy

It works fine for most month sequences but when I enter an end of month date
like 31/01/2005 and copy it down....February is missing...

Mar-05
Apr-05
May-05

Can any one explain what I am overlooking?

Thanks in advance