SAP SD GAP Analysis

Gap analysis is the study of the differences between two different information systems or applications (ex; existing system or legacy system with Client and new is SAP), often for the purpose of determining how to get from one state to a new state. A gap is sometimes spoken of as "the space between where we are and where we want to be." Gap analysis is undertaken as a means of bridging that space.
Actual gap analysis is time consuming and it plays vital role in blue print stage.
The Gaps can differ from company to company. Most commonly, however, missing functionality is industry-specific.

Examples

In customer master data the client requirement needs legacy customer number which can be solved with User exit.
In sales order we need customer Phone number, we can use user exit
If client want new field in customer master like nearest fire station.

GAP analysis is done in Blue Print stage. It aims to understand what can be done with the standard SAP and how the client actually wants a particular scenario to be processed.
It’s an understanding of the GAP between the actual & required scenarios.

Tthe difference between agreed work and completed work is GAP Analysis.

E.g.: To Fill This Gap, We Use The Enhancements,These Enhancements Divided Into Exits, Like User exits, Field Exits Screen Exits & Menu Exits.These Enhancements are used to update the standard program in its Respective Business Transactions, Used as a Gateway to Meet the Client Requirements.