If you see the books of B.Com Vs Modern Accounting Concepts you will see the difference. For example, Lets see Types of Accounting in Modern World of Accountancy.

Types of accounting are as follows:

1. Financial
2. Management
3. Cost
4. Governmental
5. Tax
6. Forensic
7. Project
8. Social


Financial Accounting, or financial reporting, is the process of producing information for external use usually in the form of financial statements. Financial Statements reflect an entity's past performance and current position based on a set of standards and guidelines like IASs & IFRSs and GAAPs

Management Accounting produces information primarily for internal use by the company's management. The information produced is generally more detailed than that produced for external use to enable effective organization control, decision making and the fulfillment of the strategic aims and objectives of the entity. Information may be in the form budgets and forecasts, enabling an enterprise to plan effectively for its future or may include an assessment based on its past performance and results. The form and content of any report produced in the process is purely upon management's discretion.

Cost accounting involves calculation and classification of cost including the application of various techniques to monitor and control costs. Its application is more suited to manufacturing concerns.
Governmental Accounting, also known as public accounting or federal accounting, refers to the type of accounting information system used in the public sector. This is a slight deviation from the financial accounting system used in the private sector.

The need to have a separate accounting system for the public sector arises because of the different aims and objectives of the state owned and privately owned institutions. Governmental accounting ensures the financial position and performance of the public sector institutions are set in budgetary context since financial constraints are often a major concern of many governments. Separate rules are followed in many jurisdictions to account for the transactions and events of public entities.

Tax Accounting refers to accounting for the tax related matters. It is governed by the tax rules prescribed by the tax laws of a jurisdiction. Often these rules are different from the rules that govern the preparation of financial statements for public use. Tax accountants therefore adjust the financial statements prepared under financial accounting principles to account for the differences with rules prescribed by the tax laws. Information is then used by tax professionals to estimate tax liability of a company and for tax planning purposes.

Forensic Accounting is the use of accounting, auditing and investigative techniques in cases of litigation or disputes. Forensic accountants act as expert witnesses in courts of law in civil and criminal disputes that require an assessment of the financial effects of a loss or the detection of a financial fraud.

Common litigations where forensic accountants are hired include insurance claims, personal injury claims, suspected fraud and claims of professional negligence in a financial matter (e.g. business valuation).

Project Accounting refers to the use of accounting system to track the financial progress of a project through frequent financial reports. Project accounting is a vital component of project management.

It is a specialized branch of management accounting with a prime focus on ensuring the financial success of company projects such as the launch of a new product. Project accounting can be a source of competitive advantage for project-oriented businesses such as construction firms.

Social Accounting, also known as Corporate Social Responsibility Reporting and Sustainability Accounting, refers to the process of reporting implications of an organization's activities on its ecological and social environment.

Social Accounting is primarily reported in the form of Environmental Reports accompanying the annual reports of companies. Social Accounting is still in the early stages of development and is considered to be a response to the growing environmental consciousness amongst the public at large


Same as many new accounting concepts have been introduced and practiced since many years but those are not incorporated in B.Com Books. I do not recommend B.Com for CSS preparation entirely, however, you may practice for numerical portion to enhance your practice