Your transaction would return you a gross take-back of 0.21 SGD x 20 x 100 = 420 SGD.
Starting from 2015 : 1 lot = 100 shares only.
If you are still referring to 1 lot as carrying 1000 shares, then your gross take-back would be 4200 SGD.
Subsequently, you would need to minus out the following charges from your transaction :-
1) Brokerage Charge. Since your transaction amt is not big, the minimum brokerage would be imposed, generally = 25 SGD.
2) Clearing and Misc Fees (can't remember the name of the third one), in your case, would not be more than, say about 3 SGD.
Hence, your net take-back would be 420 SGD - (25 SGD + 3 SGD) = 392 SGD.
If your 1 lot = 1000 shares, then your net take-back would be 4200 SGD - (25 SGD + 3 SGD) = 4172 SGD.
Hope the above helps,....
1) To be exact, most of the brokerage company charges minimum commision for $18-$25. For me, I'm using StandChart just 0.2% for commision 0.21SGD x 20 x 100 = $420 * 0.2% = $0.84 (see the huge different with $25 and $0.84 where your profit will contribute to the broker commision if your investment amount is rather small.
2) Clearing fees and GST charges. Clearing fees is charges about 0.0325% ($420 * 0.0325% = $0.136)