GSTN - The solution architecture

This is the 2nd of the 3 posts which describes IT Strategy for Implementation of GST.

A common GST portal

The solution architecture should be designed to meet the design goals for GSTN, described in the previous post. For the purpose of simplicity for taxpayers, uniformity of tax administration, digitization of all documents, and automation of related processes, it is necessary to have:

1. Common PAN-based registration 
2. Common standardized return for all taxes (with different account heads for CGST, SGST, IGST)
3. Common standardized challan for all taxes (with different account heads for CGST, SGST, IGST)

A common GST portal, operated by GSTN, is the fastest and most cost-effective way to provide common PAN-based registration, common returns, and common challans for all stakeholders. It can marry the taxpayers standard interface with the varied systems of the tax administrations. Each tax authority will have full flexibility in using this data for in-house automation, integration, and enforcement.

Basic solution architecture

Given the need for a common GST portal, the basic solution architecture is as follows:

1. Taxpayer files through a standardized taxpayer interface. 
2. States and CBEC implement tax administration systems for assessments, audits, and enforcement within their domain. This is desirable but not a pre-condition since the GSTN can provide support for states that do not have the necessary IT systems in place.
3. The taxpayer and tax authority systems are connected with a Common GST Portal, operated by GSTN.
4. Policy decisions are captured in GST Business Rules Engine that defines the tax rates, revenue sharing rules, and exceptions for all parties.

The Business Rules Engine is a component of the solution architecture that spans all entities. It codifies policies and business rules such as the rates of taxation, the revenue sharing between states and centre, a framework for exemption, and thresholds, among other things. All systems in the rest of the solution architecture will be designed so that they load business rules from the Business Rules Engine. This decoupling of the business rules from the rest of the solution architecture allows for a great deal of flexibility. At a later date, if rates are changed or new items are added to the list of taxable items, or if existing items are exempted; these changes can be reflected in the Business Rules Engine, without affecting the rest of the system. This also makes it possible to start the design and implementation of all IT systems, even while policies and rates are debated. Once the policies and rates are fixed, they can simply be reflected in the Business Rules Engine.
In addition to common registration, returns, and challans, the Common GST portal will provision for selected information needs of states.

Information Flow

The information flows are shown in Figure 5 are designed keeping the constitutional autonomy of states in mind, while simultaneously building intelligence in the system to plug leakages. The common GST portal is simply a pass-through device. The taxpayer files the return with GSTN, which keeps a copy of the return for analysis, and forwards it in near real-time to the respective state and CBEC. The taxpayer pays the actual duty in the bank, which uploads only the challan details into the GSTN. Actual funds never pass through the GSTN.
The common GST portal reconciles the returns and the challans. In addition to its pass-through role, the common GST portal also plays two other critical roles:

1. It acts as a tax booster, matching the input tax credits in the returns to detect tax evasion. It can also integrate with various other systems at MCA, CBDT for verification of PAN or other corporate information and perform data mining and pattern detection to detect tax fraud. It sends this information as alerts/ reports to the respective tax authorities. 
2. It also computes inter-state settlement, netting IGST across states.

Fund Flow

Just like the information flows, the funds flows (Figure 6) are also designed keeping the constitutional autonomy of states in mind. The design ensures smooth and timely availability of funds as soon as they are deposited. The SGST funds that are intended for the states directly go from the taxpayer to the state treasuries. Similarly, the CGST funds go directly to the centre. With the help of information from GSTN, IGST will be settled between states and centre by RBI.