In Islam, khums (Arabic: خُمْس Arabic pronunciation: [xums], literally 'one fifth') refers to the required religious obligation of any Muslims to pay one-fifth of their acquired wealth from certain sources toward specified causes. It is treated differently in Shia and Sunni Islam. This tax is paid to the imam, caliph or sultan, representing the state of Islam, for distribution between the orphans, the needy, and the [stranded] traveler.In Sunni Islam tradition, the scope of khums tax has been ghanim, which is defined as the spoils of war.
All what you have on your date of Khums is applicable for Khums calculation and payment.
The amount which you lent last year was supposed to be calculated in your Khums of last year but as it was not with you, you did not pay its Khums. When you received it back, you must pay its Khums immediately.
It's not your legal (i.e. Shar'ee) duty if you have no savings
Yes, you will find scholars who state that this type of income will also be liable for khoms when it comes to your khoms date. To be sure, check with the office of your marja or within their Islamic laws book.
May Allah grant you success
You can pay the Khums of that amount now (on the date of your Khums) if you are sure that it will be returned to you, or wait until it comes back to you then pay its Khums.
If gifts were not used for full year, khums becomes obligatory on the gifts or on its current value.
Delaying the full payment of Khums is a sinful act whether Hajj is intended or not.
Hajj is invalid if any amount used in its obligatory acts are from saved money out of which Khums is not paid fully.
Yes you can continue to pay Khums each year despite having a mortgage and adjust the monthly mortgage amount as expenses.
Khums is not our money like what we give in charity, but it is the money of others which must be given back by us to them. Half of Khums is called Sahm e Sadat and the other half is called Sahm e Imam (AS).
If your aunt is a poor Sayyed, many of our Marja’s say that poor Sayyeda can be given from the share of Sadat from Khums ; Sahm e Sadat.
If your aunt is not Sayyed, you need to seek permission from the Marja’ of Taqleed. You can easily contact the Marja’ via email or his office website.
The rulings of the marajah can differ on this, but in general, the majority allow you to give the Sahme Sadat to Seyeds (with some conditions) who don't have enough money to meet their expenses...
Double check with your specific marja first- these rulings can be found in the Risalah in the section under Khums...
Sahm e Sadat is the right of poor Sadat who are pious and practicing religion and do not have enough money or income to meet their livelihood expenses.
If the poor Sayyed is in need for marriage expenses, and has no income which can be enough for such expenses, then it will be allowed to give him from Sahm e Sadat.
Every legible expenses which you have already made, can be calculated and minus from your income for the calculation of Khums.