Tax Calculation for Indian Accounting

Tax Calculation for Indian Accounting
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according to the indian accounting system Tax Rates and Calculation is changed / product / service every year (or may remains same).

sing the OpenERP Tax system we can easily configure Tax details for the any kind of Tax, but a problem of the application of Tax, like we have to deduct the tax when we over the limit, we have to start deducting the TDS and pay to the Govt.

something like
for any service company if their total total local sales(service) go above the 8,00,000/- then they have to start adding the service tax from the next invoice and start paying to the Govt.

so in the beginning up the sales invoice (local sales and not export invoice) of 8,00,000/- if we not add the sales tax it will be ok. but after the 8,00,000/- we must add the sales tax (12% or 15% or what ever) we should add the the service type of product

this is easy to implement with the OpenERP as we have already YearSum and PeriodSum calculation from the Tax codes so based on that we can implement something to start calculation sales tax after the limit

Suggestions are welcome !!!