How can Zakat be calculated and disbursed for money that has been saved since 2010, knowing that it increases and decreases? Is it sufficient to pay Zakat on the current balance to cover the Zakat for past years? Is it permissible to disburse Zakat in a country other than the country of residence?

One must repent to Allah for any shortcomings in learning the rulings of Sharia (definition) and for failing to pay zakat (definition) on wealth that has reached the nisab (definition) for all past years, taking into account the Hijri date when the wealth reached the nisab. As for newly acquired wealth (al-mustafad), each installment of it is subject to zakat upon the completion of its own hawl (one lunar year). It is preferable to combine it with the original wealth and pay zakat on both together. If the exact amount due cannot be determined with certainty, then one must strive to ascertain it in order to clear one's liability. As for transferring zakat from one country to another, it is permissible if there is a benefit in doing so.