So in my country (Guatemala) there is one type of tax that is calculated monthly, based on the sales of the last month, I have two difficulties with the tax calculation:

1. This tax type, varies depending on the total monthly sales amount. If the sales amount is below 30,000 the tax is sales*5% (that's easy), but if the sales amount is above 30,000 the tax is (sales*7% - 600). I've already used the python plugin, but since it is applied on each individual sale (instead of the monthly sales), it is not calculated correctly.

2. This tax type is not calculated per invoice but for the whole month.

So let me give you two examples, one with monthly sales below 30k and one with a larger amount:

This is the easy example:

January 2021

Invoice 1 - 10,300 (Individually this invoice has a tax of 515 or 5% of the invoice)

Invoice 2 - 9,700 (Individually this invoice has a tax of 485 or 5% of the invoice)

Invoice 3 - 10,000 (Individually this invoice has a tax of 500 or 5% of the invoice)

Total Sales = 30,000

Since the total is below 30,000 the Tax is 5% of 30,000 so it is 1,500 or 5%. If you calculate it for every invoice, it also works since it is a fixed amount of 5%.

This is the scenario I'm stuck with:

February 2021

Invoice 1 - 20,300 (Individually this invoice has a tax of 1,218 or 6% of the invoice)

Invoice 2 - 19,700 (Individually this invoice has a tax of 1,182 or 6% of the invoice)

Invoice 3 - 20,000 (Individually this invoice has a tax of 1,200 or 6% of the invoice)

Total Sales = 60,000

Since the total sales are above 30,000; the tax is 7% of 60,000 minus 600 so it is 3,600 (or 6%, but this % changes depending on total sales). Individually it is impossible to calculate the tax, since you don't know the total sales of the month when you are creating each invoice individually.

So, I've not found anywhere on Odoo can I configure a tax on total sales (or how to do it) or how to manually calculate and add the tax into the ledger.

Any further feedback is greatly appreciated!