Could you please tell me the BEST time to do an accounting Pre-audit? (1st qtr.
Mid-year, 3rd qtr)..

Does make any sense to conduct a pre-audit in the 12th month of the fiscal
Year?

Is the pre-audit cost suppose to reduce the cost for the full audit at the
End of FY?

The best time is very subjective. If you currently have spare time in your schedule so that you do not cause undue hardship for the other functions in the business, then now would be a good time. If you have strong internal controls over your accounting processes, then it is easier to rely on early pre-audit testing and rely on the controls to maintain. If you do not, then early pre-testing could identify problems for you that could be corrected sooner than later. However, until there are adequate internal controls, the year end audit will require additional tests and the pre-audit will not have a significant impact(reduction) in that work.