Share capital consists of all funds raised by a company in exchange for shares of either common or preferred stock. The amount of share capital or equity financing a company has can change over time. A company that plans to raise more equity can be approved to issue additional shares, thereby increasing its share capital.

The difference between called-up share capital and paid-up share capital is that investors have already paid in full for paid-up capital. Called-up capital has not yet been completely paid, though payment has been requested by the issuing entity.

Depending on the situation, share capital can fall into one of four categories.

1. Authorized Share Capital

To sell stock to the public, a business must first register with a governing body. Part of this registration includes documentation of the amount of capital the business is looking to generate through selling stock. This amount is called its authorized capital and is the maximum amount that can be raised in this manner. 

2. Issued Share Capital

Out of the maximum amount of authorized share capital, the value of shares the company actually issues is called issued share capital. The amount of issued share capital is generally much lower than the authorized share capital so the business has the opportunity to issue additional shares later.

3. Called-Up Capital

Depending on the jurisdiction and the business in question, some companies may issue shares to investors with the understanding they will be paid at a later date. This allows for more flexible investment terms and may entice investors to contribute more share capital than if they had to provide funds up front. The amount of share capital owed by shareholders, but has not yet been paid, is referred to as called-up capital.

4. Paid-Up Capital

Any amount of money that has already been paid by investors in exchange for shares of stock is paid-up capital. Even if an investor has not paid in full, the amount already remitted is included as paid-up capital. All paid-up capital is listed under the shareholders' equity section of the issuing company's balance sheet.