5.
A registered person has to file LUT for availing zero rating on export transactions. To avail zero rating, two conditions are listed in the LUT 1) The goods needs to be exported out of India within 3 months from the date of issue of Invoice. 2) The payment for services must be received in convertible foreign currency within 1 year from the date of issue of invoice. The first condition is pertaining to goods and the second condition is pertaining to services.
In your case, if payment for the service is not received within 1 year from the date of issue of invoice, then you are liable to pay tax on the export turnover along with Interest @18% as you have not fulfilled the conditions of the LUT for zero-rating.
Now coming to the aspect of registration, the supply of software services effected by you is an Inter-state supply of Service. Therefore you are required to be registered without any threshold benefit. The consequence of not taking registration is 1) You may receive notice u/s. 63 for assessment of unregistered persons within 5 years from the due date of filing annual return of the year of export 2) liable for penalty u/s. 122(xi) of an amount ₹ 10,000/- or 10% of tax due whichever is higher.
Therefore if you have received the payment for the exports completed within the time prescribed, then you may be liable only for the penalty for non-registration. However you may receive notice ASMT - 14 for assessment of unregistered persons upto 5 years. Hope this helps...