Answered by Shaykh Yūsuf Badāt
Assalamu Alaykum, I had a question regarding Forex.
On one of your previous Fatwas relating to Forex, you have stated the following, “However, for the transaction to be valid, it would be necessary that the transaction is either completed on a spot basis or at least one party takes possession of the currency at the time of the transaction. Separating with debt on both sides (deferred to a future date) is not permitted.”
In terms of the above, as Forex is done online now, the trade once placed, is completed in the sense that it is created/opened on the spot and the trader who places this trade has control of this as they can close the trade when they want or keep it open and this is done hand in hand but online. I just did not understand the part where you said ‘separating with debt on both sides deferred to a future date is not permitted.’ What did you mean by this? From my understanding, the trade is made immediately on the spot and no date is set in the future for when this trade will close.
If you could provide clarity on this matter it would be much appreciated.
بِسْمِ اللَّـهِ الرَّحْمَـٰنِ الرَّحِيمِ
In the Name of God Most Merciful, Most Kind
Wa Alaykum Salām/ Greetings of Peace
Thank you/ Jazāk Allāh Khayr for contacting Mathabah with your query.
In response to your question, kindly note that forex trading online would require the transaction to be completed on the spot as you have described.
The meaning of the condition “separating with debt on both sides deferred to a future date is not permitted.” refers to the fact that the parties doing the transaction cannot leave or log off the online transaction with the promise to make the payment later.”
‘Obāda Ibn Ṣāmit (may God be pleased with him) reported God’s Messenger (peace and blessings be upon him) as saying, “Gold is to be paid for by gold, silver by silver, wheat by wheat, barley by barley, dates by dates, and salt by salt, like for like and equal for equal, payment being made on the spot. If these classes differ, sell as you wish, if payment is made on the spot.” – (Ṣaḥīḥ Muslim) 
Only Allāh knows best
 عَنْ عُبَادَةَ بْنِ الصَّامِتِ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «الذَّهَبُ بِالذَّهَبِ وَالْفِضَّةُ بِالْفِضَّةِ وَالْبُرُّ بِالْبُرِّ وَالشَّعِيرُ بِالشَّعِيرِ وَالتَّمْرُ بِالتَّمْرِ وَالْملح بالملح مثلا بِمثل سَوَاء بسَواءٍ يَدًا بِيَدٍ فَإِذَا اخْتَلَفَتْ هَذِهِ الْأَصْنَافُ فَبِيعُوا كَيْفَ شِئْتُمْ إِذَا كَانَ يَدًا بِيَدٍ» . رَوَاهُ مُسلم