If the index regulation is to be zero going forward, the index must be set equal to the base index for all future months. You do this by editing the forecast values on the index.
How to do it
Go to Index regulation and open the index.
Click Edit above the index table.
Scroll down to the rows with Estimate in the Source column, and set the value in the Index column for each upcoming month equal to the base index.
Save and check that the index regulation going forward is zero.
Why isn't it enough to leave the index fixed?
If the index stays fixed at its current level, there will still be index regulation. AIMZ calculates with the difference between the base index and the latest known index on all future installments. Only when the forecast equals the base index does the index regulation become zero.
Good to know
You only change the forecast values going forward. Actual index values (source SSB) are not affected.
If you only want zero index regulation against one party, you can create a separate variant of the index.