Re: If I make payment according to the payment arrangement plan.
Broadly, yes. In British English, per cent is often written as two words. Also, I would say, "make payments", or simply "pay", rather than your "make payment". You also need a comma before "then".
Originally Posted by Jit833
So, I would write these sentences as:
If I pay according to the payment arrangement plan, then I will be given ten per cent off.
If you keep your promise and make payments according to the payment arrangement plan, then you will be eligible for ten per cent off.
Finally, you could always write "ten percent" as "10%", which many people would prefer.
I'm not a teacher of English, but I have spoken it for (almost) all of my life....