**Preliminary expenses not written off** appears under the head of **Reserves and Surplus** in the balance sheet.

**Reserves and Surplus:**
- Reserves and surplus is a category in the balance sheet that represents the accumulated profits or reserves of a company.
- It includes various types of reserves and profits that are not distributed as dividends to the shareholders.
- This category reflects the financial strength and stability of the company.

**Preliminary expenses:**
- Preliminary expenses are the expenses incurred by a company before its incorporation or during the process of setting up the business.
- These expenses include legal fees, registration fees, printing and stationery expenses, promotional expenses, etc.
- Preliminary expenses are considered as intangible assets and are amortized over a period of time.
- Amortization is the process of gradually reducing the value of an intangible asset over its useful life.

**Preliminary expenses not written off:**
- When a company incurs preliminary expenses, it can choose to write off these expenses immediately or amortize them over a period of time.
- If a company decides not to write off the preliminary expenses immediately, it shows the remaining balance of these expenses under the head of "Preliminary expenses not written off" in the balance sheet.
- This indicates that a portion of the preliminary expenses is still considered as an asset and has not been fully amortized.
- The amount of preliminary expenses not written off represents the unamortized balance of these expenses.

**Significance:**
- The presence of preliminary expenses not written off in the balance sheet indicates that the company has incurred significant expenses during the setup or incorporation phase.
- It also suggests that the company has chosen to spread the cost of these expenses over a longer period rather than writing them off immediately.
- This can have an impact on the profitability and financial position of the company as it affects the calculation of net profit and reserves.

In conclusion, preliminary expenses not written off appear under the head of reserves and surplus in the balance sheet. It represents the remaining balance of the preliminary expenses that have not been fully amortized. This category reflects the financial strength and stability of the company and provides insights into the company's past expenses and future profitability.