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.
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.
Once you have paid the khums on an amount of money, that money will be exempt from any further khums.
According to Sayyid Sistani(may Allah lengthen his life) if one doesn't have a fixed job and a regular salary, he must take into account whatever he acquires for a year and if it doesn't get spent in his year's expenses, he should give one-fifth of it as Khums. So it's going to be a distinct "Khumsi Year" for each belonging, possession or finance you may get.
The Persian reference is :
Q no: 2301
Khums is not obligatory on you if you have no savings at all after receiving your annual income and spending in your lawful usual expenses. If you have any savings no matter how much, then Khums is obligatory on that savings once per year. After paying the Khums from any amount, the remaining amount is called Mukhammas (Khums paid) and this Mukhammas amount is exempted from Khums in the coming years as far as it remains with you.
1. We abide to the meanings of Quranic verses and rules of Islam as explained by the Prophet Muhammad (SAWA) and his Holy Progeny Ahlul Bayt (AS), and not our own thinking or our superficial linguistic understanding which is away from what the Prophet and Ahlul Bayt have explained.
2. Khums consist of two equal parts; Sahm Imam, and Sahm Sadat. Sahm Sadat is the right of needy Sadat who ae from the family tree of the Prophet (SAWA). Allah (ST) knows that Ahlul Bayt (AS) and their families will face big difficulties from their enemies, that is why, Sahm Sadat has been ordained for the needy Sadat.
3. Sahm Imam (AS) is the right of the Imam (AS) and it is received either by him or by his deputies like the Marja' of Taqleed or his deputies now a days. Sahm Imam is used generally in serving the general poor and needy and religious, educational and social services.
It is very simple and easy to calculate Khums. It is just to calculate how much you have remaining cash in hand or bank or with people, and property except your residence, and remaining unused items. You calculate the total and take 20% which is the Khums.
A woman, single or married, is independent in her takaleef and obligations towards Allah ta'ala, even in financial matters.
A wife is not obliged to financially contribute to household expenditures, however she is able to do so out of her kind generosity and good-will. She is able to count that as her common expenses.
As for long-term loans, and her contributing to getting it paid of, it will not exempt her from khums should she have anything entitled for khums on her khums day.
And Allah knows best.
This question is very broad, and I would firstly recommend that you do some reading on the background of Khums and its rulings.
A very brief reply to your two questions:
1. What items is khums compulsory on: (1) savings at the end of your khums year, and (2) items that you own but are new and have not been used all the way until the arriving of your khums day.
2. How should it be distributed: To be given to the office of your Marja' Taqleed, or his shar'i representative (wakil).
There are much more details, and as this is a fiqhi issue, you will need to refer to the fatwas of your Marja' Taqleed. I would recommend you go through this link, and familairise yourself with the topic: