Microsoft Support Request #3831958 detailed the issue of fixed asset additions not following the same depreciation rules as the original fixed asset.  The issue was described as follows:

- NEW ACQUIRED FIXED ASSETS should be depreciated as follows
o If the posting date of the new fixed asset is before 15th of the month, then depreciation starts the first of the month (in AX referred to as mid month (1rst of month)  for depreciation convention)
o If the posting date of the new fixed asset is after 15th of the month, then depreciation starts the first of the following month

- EXISTING FIXED ASSETS
o When additions are made to current fixed assets, then it should follow the same rule as “new” fixed assets
o However, the system is not behaving this way.
o For additions to fixed assets, the depreciation starts the first of the month no matter when the “newly acquired piece” is posted.

An example is as follows:
- NEW FIXED ASSET
o Create a new fixed asset
 ie BLAD-0016
 Vendor Microtec – invoice amount $20K (assume no taxes)
 Posting purchase date April 18
 Depreciation starts May 1

o EXISTING FIXED ASSET ADDITION
 ie BLAD-0015
 Vendor Microtec – invoice amount $20K (assume no taxes)
 Posting purchase date April 18
 Depreciation starts April 1

As you can see from the existing asset example, the Depreciation Start date does not follow the defined depreciation convention.

Microsoft responded with the following workaround:

Create an additional asset in which one would track the new acquisition price and the service life.

Another option is to use 'Create depreciation adjustments with basis adjustments' on the asset's book. With this option, once you post an additional acquisition, a depreciation adjustment will be calculated to cover periods between the original acquisition and the additional acquisition for the amount based on the additional acquisition amount.

As a product improvement, we would like to suggest that fixed asset additions have the ability to use the defined depreciation convention that is set on the original fixed asset.