is the legal in islam Intraday trading involves buying and selling of stocks within the same trading day
In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
Respected Brother in Islam
Day trading is the buying and selling of various financial instruments with the goal of making a profit from the difference between the buying price and the selling price within the same day.
There are different techniques/Strategies adopted in intraday trading. One of the most common technique is Short Selling.
Short sale is a market transaction in which an investor sells the shares before buying it, in anticipation for stock price to decline in the future. After selling these stocks, he awaits for the price to decline to the desired amount upon which he purchases the shares. The main focus of day traders is profiting from short-term price fluctuations and not the subject of sale itself.
Intraday Short Sale strategy is not permissible because the trader sells stocks that he does not own.
Likewise, other intraday techniques whereby the trader sells stocks before taking possession of the stocks is also not permissible. 
You may refer to the conditions for trading in shares and stock market below. Intraday violates the fifth condition.
Conditions for trading in stock market
1. The main business of the company is not in violation of Shariah. Therefore, it is not permissible to acquire the shares of the companies providing financial services on interest, like conventional banks, insurance companies, or the companies involved in some other business not approved by the Shariah, such as the companies manufacturing, selling or offering liquors, pork, haram meat, or involved in gambling, night club activities etc.
2. If the main business of the companies is halal, like automobiles, textile, etc. but they deposit there surplus amounts in an interest-bearing account or borrow money on interest, the shareholder must express his disapproval against such dealings, preferably by raising his voice against such activities in the annual general meeting of the company.
3. If some income from interest-bearing accounts is included in the income of the company, the proportion of such income should be given in charity and must not be retained by him. For example, if 4% of the whole income of a company is accrued from interest-bearing deposits, then 4% of the dividend should be given in charity.
4. The shares of a company can be purchased only if the company owns some non-liquid assets. If all the assets of a company are in liquid form, i.e. in the form of money, then that cannot be purchased or sold, except on par value, because in this case the share represents money only and the money cannot be traded in except at par value.
5. If one engages in trading, then it is necessary to ensure that the delivery of the stock has been made before selling it off to another buyer. He cannot sell without taking the possession of the share. 
And Allah Ta’āla Knows Best
Anas Sharieff Qasmi.
Student Darul Iftaa
Checked and Approved by,
Mufti Ebrahim Desai.
اگر کمپنی کا کاروبار خلاف شرع نہ ہو تو شیئرز خریدنے میں کوئی حرج نہیں [فتاویٰ عثمانی :٣/١٧٧
An introduction to Islamic finance: 207/8
الأصل للشيباني ط قطر (2/ 436)
وإذا باع الرجل بيعاً قد كان اشتراه قبل أن يقبضه أو اشترك فيه أو ولاه فإن هذا مردود لا يجوز. قال محمد: حدثنا بذلك أبو حنيفة رفعه إلى النبي – صلى الله عليه وسلم – أنه نهى عن بيع ما لم يقبض .
فتاویٰ عثمانی :٣/١٨٥
اس وقت تک شیئرز کو آگے بیچنا جائز نہیں ہے جب تک ڈلیوری نہ مل جائے.اگر بچنے والے نے شارٹ سیل کی ہے یعنی شیئرز ملک میں لاۓ بغیر فروخت کئے ہیں تو یہ بیع ہی باطل ہے.
 عن حكيم بن حزام قال قلت يا رسول الله الرجل يسألنى البيع وليس عندى أفأبيعه قال لا تبع ما ليس عندك – ابن ماجه
عن عمرو بن شعيب عن أبيه عن جده قال نهى رسول الله صلى الله عليه وسلم عن سلف وبيع وعن شرطين فى بيع واحد وعن بيع ما ليس عندك وعن ربح ما لم يضمن – سنن النسائى ، مسند أحمد
If you buy shares of Microsoft (MSFT) on Friday, June 2, 2017, while your broker would debit your account for the total cost of the investment immediately after your order is filled, your status as a shareholder of Microsoft will not be settled in the company’s record books until Tuesday, June 6th. Therefore, the settlement date is the date in which you become a shareholder of record. Note that weekends and public holidays are not included. In this case, if Monday was a public holiday, the settlement date would be Wednesday, June 7th.
A shareholder is considered to be any entity that has legal ownership of a company’s shares. Having legal ownership means being recorded as the shares’ owner by the company: When you buy a stock from another investor, three days after the transaction has occurred your name will appear in the company’s record books, and you will be deemed the holder of record. The investor from whom you purchased the shares will at the same time be removed from the records. https://www.investopedia.com/ask/answers/167.asp
 Note: Stocks that reflect in one’s trading account on the trade day after the purchase does not necessarily means possession. It takes 2-3 business days [approx.] for the delivery to take pla