When is an assessment u/s 143(3) said to be completed?

From Section 143(3), you can interpret that when the Assessing Officer makes an assessment of the Total Income or Loss of the Assessee, by order in writing, and determines the sum payable by him or refund due to him, on the basis of the information and explanations furnished to the AO, then assessment under this section is said to be completed.

In this case,in my opinion, the issue of order to pay taxes by the AO, can be said to mark completion of assessment.