Hello,

The tax is calculated as following

```
Exclusive Tax = (price * tax rate / 100) => (100 * 25 / 100) = `25`
so product nett price 100 & unit price will be 125

Inclusive Tax = (price * tax rate / (100 + tax rate)) => (100 * 25 / (100 + 25)) = `20`
so product nett price 80 & unit price will be 100
```

If you want to change these, you will need to edit `themes/default/assets/js/custom.js` around line 241 for front-end javascript calculation and `app/models/Sales_model.php` around line 524 for back-end php.

Thank you

Can you help me change this? I am beginner :)

in sales model i change

```
if ($tax_method == 'inclusive') {
$item_tax_amt = $this->sim->formatDecimal((($net_unit_price * $tax_details->rate) / (75+$tax_details->rate)), 4);
$item_tax_val = $tax_details->rate."%";
$net_unit_price -= $item_tax_amt;
} else {
$item_tax_amt = $this->sim->formatDecimal((($net_unit_price * $tax_details->rate) / 75), 4);
```

in cusom.js i change to

```
if (tax_method == 'inclusive') {
product_tax = formatDecimal(((net_unit_price * this.rate) / (80 + this.rate)), 4);
net_unit_price -= product_tax;
} else {
product_tax = formatDecimal(((net_unit_price * this.rate) / 80), 4);
```

Now is show same vat number :) but is show only on new invoice not on old invoice is it correct? And is it correct with 80 and 75?

Hello,

I am not sure how you need it and how your country calculate the inclusive tax. Once you have formula you can apply as you mentioned above. It will apply to all new sales.

To apply it to old sales, you will need to edit them. Once submitted the tax will be calculated same as for new sales.

Thank you