I am trying to compare two percentages and produce a third percentage

for example

The Threshold (column B) is the expected standard
The Availability (Column A) is the actual received
The Credit (Column C) is the percentage discount given dependant on the difference between columns A and B

screengrab

Formula used

I’ve attempted to use a formula to say if the value in A is less than the value is B minus the requested percentage then display the text but it does move from the first IF statement

=IF(A4=””,””,IF(A4<=B4-1%,”5%”,IF(A4<=B4-3%,”15%”,IF(A4<=B4-5%,”20%”,”N/A”))))

Nothing seems to work, any pointers would be greatly appreciated

What I want to happen

If the availability is up to 1% below the threshold 5% would be displayed
If the availability is up to 3% below the threshold 15% would be displayed
If the availability is up to 5% below the threshold 20% would be displayed

What I’ve tried

I’ve tried nesting =IF(A4=””,””,IF(A4<=(B4-1%),”5%”
I’ve tried numerical =IF(A4=””,””,IF(A4<=(B4-0.01),”5%”

Nothing seems to work, any pointers would be greatly appreciated