1. Average service life method: annual depreciation amount = (original price-estimated net salvage value)/estimated service life = original price x( 1- estimated net salvage value/original price)/estimated service life = original price x annual depreciation rate.

2. Workload method: unit workload depreciation = original price of fixed assets x( 1- estimated net salvage value rate)/estimated total workload.

3. Double declining balance method: annual depreciation = net fixed assets at the beginning x2/ expected service life.

4. Sum of years method: annual depreciation amount = (original price-estimated net salvage value) x annual depreciation rate.

Characteristics of fixed assets:

1, the value of fixed assets is generally relatively large, the use time is relatively long, and they can participate in the production process repeatedly for a long time.

2. Although wear occurs in the production process, it does not change its physical form, but gradually transfers its value to the product according to its wear degree, and the value transferred part is recovered to form a depreciation fund.

As a monetary form of fixed assets, fixed funds also have the following characteristics:

1, the period of fixed capital is relatively long, which does not depend on the production cycle of products, but on the service life of fixed assets.

2. The value compensation and physical renewal of fixed funds are carried out separately. The former is gradually completed with the depreciation of fixed assets, and the latter is realized by using the depreciation funds accumulated at ordinary times when the fixed assets are unusable or unsuitable for use.

3. When purchasing and building fixed assets, you need to pay a considerable amount of monetary funds. This investment is one-off, but it will be recovered by stages through depreciation of fixed assets.

To sum up, the depreciation methods of fixed assets include life average method, workload method, double declining balance method and sum of years method. Once the calculation method of depreciation of fixed assets is determined, it shall not be changed at will.

Legal basis:

Article 27 of the Measures for Pre-tax Deduction of Enterprise Income Tax in People's Republic of China (PRC)

The straight-line depreciation method is used to calculate the depreciation of fixed assets that taxpayers can deduct.

Article 31

Taxpayers' expenses for repairing fixed assets can be deducted directly in the current period. Taxpayers' expenditure on the improvement of fixed assets can increase the value of fixed assets if the related fixed assets have not been fully depreciated; If the relevant fixed assets have been fully depreciated, they can be used as prepaid expenses and amortized evenly within a period of not less than 5 years. The repair of fixed assets that meet one of the following conditions shall be regarded as the expenditure for the improvement of fixed assets:

(a) the repair cost reaches more than 20% of the original value of fixed assets;

(2) After the repair, the economic service life of related assets is extended for more than two years;

(three) the fixed assets after repair are used for new purposes or changed.