Is Zakat obligatory on a sum of 6 million Iraqi Dinars that has been held for more than a year and a half, or on the current sum of 4 million Iraqi Dinars, knowing that the Zakat nisab in Iraqi Dinars is 7 million Dinars, while the nisab differs when calculated by silver? And are the installments paid so far as Zakat (150,0 Iraqi Dinars) sufficient for the first year?

The threshold (nisab (definition)) for Zakat (definition) is approximately 85 grams of gold or 595 grams of silver. The silver nisab is what is considered, as it is the lower of the two thresholds. Zakat is obligatory on saved wealth if a full lunar year (hawl) has passed since it reached the nisab. The amount due is one-quarter of one-tenth (2.5%). If wealth reaches the nisab and a hawl passes, Zakat becomes immediately obligatory. It is not permissible to delay or pay in installments for one who is able to pay it. Since you paid one hundred and fifty thousand, you are considered to have paid Zakat for the past year. You must verify whether your wealth reaches the nisab in the new year to pay its Zakat at the time it becomes due.