1) Sure you can issue an invoice withour sales tax numbers.
2) It depends on your terms of sale. If you have mentioned octroi to be payable by buyer, than it is buyers responsibility to pay octoi. If you have listed inclusive of all taxes and duties, than you have to pay octroi.
3)Used personal goods do not incurr sales tax / vat.
4) Most, if not all courier companies will pay octroi can collect it from the buyer. If you have a credit account with the courier company, they will collect octroi from you on request.
5) All courier companies accept used items.
This is the opinion of a lay fellow seller. If you want totally accurate information you should consult you
Tax Advisor.
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