Sorry the question is not clear

The flat file or a csv file contains the data of the client.

May be your question is he is not giving in a flat file 
format.  By taking the data available from him u have to 
create a flat file to load into interfaces.

then wat will u convert dear?

we will develop the program as per the technical document 
we have and we will ask the client to provide the flat file.

with out flat file how can u develop the interface or 
conversion. To develop this we required cv040 document, 
excel file or flat file.

as per my knowledge it is not possible to create an 
interface without any flat table.
so a flat file is surely required to develope an interface.

In practical scenario, we usually get the interface data in 
flat file during the QA testing phase of the project. 
During the Initial Development the Developer will create a 
sample data flat file based on the technical design 
document data mapping layout for unit testing of the code.
This code will be fine tuned based on the actual flat file 
received from the client for testing.

There will be less code changes if the client communicates 
the exact columns/lengths and their positions in the flat 
file to the functional/technical designer.

Lot of interface data/code errors are due to 
miscommunication between the 
client/Business representative
==> Functional Design Document 
==> Technical Design Document 
==> Final Interface Code

Thanks,
Shashi