Below is an extract from GST Q & A :
Question : Whether a full handwritten tax invoice can be issued by a registered person?
Answer : Beginning 1st October 2015, the registered person excluding ‘retailers’ must use a computer generated invoice or pre‐printed invoice which is GST compliant.
In the case of ‘retailers’, they must use a GST compliant point of sale (POS) system or a GST compliant cash register to issue GST tax invoices beginning 1st October 2015.
The ‘retailers’ in this item refers to the following categories of businesses –
(a) Hardware shop.
(b) Restaurant including coffee shop.
(c) Mini market, grocery and sundry shop.
(d) Book store.
(f) Places of entertainment.
A GST registered person is not allowed to issue any handwritten tax invoices.