Created attachment 162481 [details]
calculation sheet for the proposed formula

I have an idea about a new financial formula which i am not sure why no one has implemented yet, maybe it is in the pipeline but i am putting this out.
Libreoffice currently has a variety of depreciation formulae, db, ddb, amordegrc, amorlinc,sln, syd, vdb and there may be more but i have been unable to find a suitable formulae that gives me the depreciation amount as needed.
One of the accepted methods of calculating depreciation is on "reducing balance method" whereby, for the sake of simplicity and replicability, a predefined rate of depreciation is given. Say, building is to be depreciated at 10% WDV or written down value. Basically, an asset is taken at cost value and a rate of depreciation is reduced from this value during the year and the closing balance for that year becomes opening balance of next year and  the rate of depreciation is applied on that new opening balance and so on until either the asset is scrapped or its value is reduced to zero, in which case, the asset is said to be fully written off.
For example, i have set the cost of asset at 100,000 and applied a depreciation rate of 60% over the lifetime of the asset. As you can see, each line represents one year and opening balance of first year is reduced by 60% and that closing balance becomes opening of next year.




I propose that we have a formula, WDV (cost,rate of depreciation,period of calculation).

Also, a second WDVD formula to find the depreciation value for a given year WDVD (cost,rate of depreciation,period of calculation). 

Calculations are assumed to be at the end of period because that is the norm.

i have attached a sheet explaining with simple case values the need for this formula, if i wanted to find written down value of an asset, say 3 years in a line, i have to make a chart plotting each year and then going at it one by one. These formulas would be immensely helpful for users working with financial statements, etc.

For comparison, https://www.wallstreetmojo.com/written-down-value-method/
this is a link to a blogpost explaining how to calulate this WDV in excel. Note that it is to be calculated on a per year basis and you cannot just jump to year 7 in the example of the blog. you must calculate the values one after the other.

This formulae is different from existing depreciation functions because they all assume the user knows about the useful life of the asset. Here, all you need is rate of depreciation. Also, when i mentioned "cost" in the formula, it is assumed to be "cost-residual value" as is the norm so it need not be mentioned again in the formula.

This is mostly used for finance/ taxation purposes where a standard depreciation rate is given by the revenue departments to keep people from charging all the value of asset to profits, in hopes of reducing the tax liability.