Example
Consider the manufacture and sale of any item, which in this case we will call a widget. In what follows , the term "gross margin" is used rather than "profit". Profit is only what is left after paying other costs, such as rent and personnel.
Without any tax* A widget manufacturer spends $1.00 on raw materials and uses them to make a widget.
* The widget is sold wholesale to a widget retailer for $1.20, making a gross margin of $0.20.
* The widget retailer then sells the widget to a widget consumer for $1.50, making a gross margin of $0.30.
With a North American (Canadian provincial and U.S. state) sales tax
With a 10% sales tax:* The manufacturer pays $1.00 for the raw materials, certifying it is not a final consumer.
* The manufacturer charges the retailer $1.20, checking that the retailer is not a consumer, leaving the same gross margin of $0.20.
* The retailer charges the consumer $1.65 ($1.50 + $1.50x10%) and pays the government $0.15, leaving the gross margin of $0.30.
So the consumer has paid 10% ($0.15) extra, compared to the no taxation scheme, and the government has collected this amount in taxation. The retailers have not paid any tax directly (it is the consumer who has paid the tax), but the retailer has to do the paperwork in order to correctly pass on to the government the sales tax it has collected. Suppliers and manufacturers only have the administrative burden of supplying correct certifications, and checking that their customers (retailers) aren't consumers.
With a value added tax
With a 10% VAT:* The manufacturer pays $1.10 ($1 + $1x10%) for the raw materials, and the seller of the raw materials pays the government $0.10.
* The manufacturer charges the retailer $1.32 ($1.20 + $1.20x10%) and pays the government $0.02 ($0.12 minus $0.10), leaving the same gross margin of $0.20.
* The retailer charges the consumer $1.65 ($1.50 + $1.50x10%) and pays the government $0.03 ($0.15 minus $0.12), leaving the gross margin of $0.30 (1.65-1.32-.03).
With VAT, the consumer has paid, and the government received, the same as with sales tax. The businesses have not incurred any tax themselves. Their obligation is limited to assuming the necessary paperwork in order to pass on to the government the difference between what they collect in VAT (output tax, an 11th of their sales) and what they spend in VAT (input VAT, an 11th of their expenditure on goods and services subject to VAT). However they are freed from any obligation to request certifications from purchasers who are not end users, and of providing such certifications to their suppliers.
Note that in each case the VAT paid is equal to 10% of the gross margin, or 'value added'.
The advantage of the VAT system over the sales tax system is that under sales tax, the seller has no incentive to disbelieve a purchaser who says it is not a final user. That is to say the payer of the tax has no incentive to collect the tax. Under VAT, all sellers collect tax and pay it to the government. A purchaser has an incentive to deduct input VAT, but must prove it has the right to do so, which is usually achieved by holding an invoice quoting the VAT paid on the purchase, and indicating the VAT registration number of the supplier.
http://en.wikipedia.org/wiki/Value_added_taxThere are two problems with a VAT in the US (as opposed to Europe where it supports a very progressive social safety net). The VAT (like a sales tax) taxes consumption rather than production (income tax is, at least in theory, based on taxing your economic productivity rather than what you do with it). It plays a role in making European economy less reliant on overconsumption compared to the US. The more one saves rather than spends, the less taxes one pays.
One with a VAT in the US is that it would have to be counterbalanced by tax cuts in other areas to avoid a huge tax increase for middle and lower income people. That may not be possible or politically feasible.
The other is that it is inherently regressive unless it is structured to deal with the disproportionate impact on poor people. In Europe it may not be so bad if a regressive tax is used to support a progressive social safety net. At least the poor there get value for their money. But in the US such a regressive tax would be tied to a regressive social safety net. Hardly a good deal for the poor.
Either the VAT would have to be restructured to make it less regressive or the proceeds would have to tied to making our social safety net more like that of Europe.