"multi-point" means that it is applied at multiple stages during the production, distribution and sale of goods -- every time something passes from one person or company to the next. "set-off" means that tax paid on purchases is subtracted from tax due on sales, so you effectively only pay tax on the value that you have added (hence the name "Value Added Tax"). (Disclaimer: If you need to understand this for a serious financial purpose then you should get advice from a qualified professional.
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