RE: End of year Vs. Transactions posting
Closing the year is recommended to be conducted at the year end date 31/12/....Although, mostly in all the companies I have worked with, no company could be able to close precisely at the last day of the year because of outstanding documents to be entered, reconciliation and many other reasons, which simply push the financial closing way after 31/12.
Therefore, before closing the year, you could change the system date on Dynamics GP to 13/12/...
To get back to your question, and provide a simple justification on why that's a recommendation. Let me provide a simple example, In inventory Closing, all sales transactions are calculated and the summary "Quantity Sold" value is provided for each item in inquiry. On the inventory closing, this value will be reset to zero. Suppose you close the year at 28/2/ the following year, the value of the new sales documents will be included in the "reset", and the value will be zero.
Several other justifications could be provided, which makes closing the year at the 31/12 is a best practice.