On the Lease Agreement Card if you have selected Interest Implicit in Lease, you will be able to enter Lease liability at Commencement. The system will then provide an Interest Rate amount, based on payments and term to fit.

In the example above, Lease Liability on Commencement was entered as 18000. The system (based on provided payments and term) calculated, that the Interest Rate should be equal to 6,559…

You are free to change the value of Interest Rate at this stage - will consequentially change Lease Liability. If it does not match to your external calculations, you can try to change the Interest Calculation Formula at Lease Setup Interest.