I am a Qualified Chartered Accountant from India and would like to highlight some more important things with regards to GST:
In case of inter state supply (including export of services/goods) the exemption limit of 20 Lac is not available and one has to get registerd to GST.
If you have been providing services to your foreign clients since July 01, 2017 you should get yourself registered in GST atleast by July 30, 2017. This is must.
There are 3 returns to be filed every month.
You can also claim GST on expenses incurred while providing services to your clients.
For your services to be treated as "Export Services", you will have to make sure that the funds arrives in India in foreign currency. So, on Upwork you should choose, wire transfer in USD as "Payment Method".
You will have to arrange for Foreign Inward Advice from your bank, to prove that the money came in India in foreign currency and hence is agains export of services.
The money for your export services (coming from Upwork/Paypal/Bank Account of your client) should come in a current account (not a saving account). Otherwise you will not be able to get the Foreign Inward Advice.
Not getting registered in GST and ingoring criticalities of the GST law can lead to hugh tax, interest and penalties (even prosecution).
All the freelancers should take action on time to keep their hard earn money and themselves safe.
**Edited for Community Guidelines**
CA. Ankit Tulsyan