Add tax
or tax included?

The price already contains tax. To find the tax, divide the total by 1 plus the tax rate, then subtract the net amount.

Use add tax when your prices exclude tax; use included when the agreed price is the final amount the client pays.

Two different calculations. Use the one that matches what you agreed with the client.

中文说明

价外税：明细不含税，税额另加；含税：客户看到的总价已含税，税额要从总价里倒算，不能再次加税。下面有 $1000/10% 的具体例子。

Your prices exclude tax. The client pays the line items plus tax.

subtotal = 1,000
discount = 0
tax 10% = 100
total    = 1,100

With a 10% discount: base = 900, tax = 90, total = 990.

The agreed total already contains tax. The tax is the part inside the total, not an extra line.

total    = 1,000
net      = 1,000 / 1.10 = 909.09
tax 10%  = 1,000 - 909.09 = 90.91

With a 10% discount: total = 900, net = 818.18, tax = 81.82.

Adding 10% on top of a tax-inclusive total. A $1,000 inclusive total does not become $1,100; the tax is already inside the $1,000.

The invoice generator has both modes: Add tax on top and Tax included. It shows the tax inside the total when you choose included.

What does tax included mean?
The price already contains tax. Divide the total by 1 + rate to find the net; the difference is tax.

Which mode should I use?
Add tax if your prices exclude tax; included if the agreed price is the final amount.

Estimate only; not tax advice. Rules differ by country.