Handling taxes
If the product or service you sell attracts taxes, you can specify that while adding the product or service. This tax will automatically get reflected when you raise invoice with that particular item. Alternatively you can also specify the tax while raising the invoice.

Handling Discounts
Discounts can be specified for the product or service while raising invoice. Discounts can be specified at a individual product or service level.

Handling other financial charges
If selling the product or service involves additional financial charges like freight, packaging etc. the best way to handle it will be to add it as another item while raising the invoice.
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