4个回答
应该将这2 句组合一起：
都已经发货这么久了，根据以往的付款记录，都显示你有很好的信誉，你怎么还不把余款付清？
It has been quite some time since we delivered the goods; your previous payment records show that you have a good reputation, so we wonder why you have yet to settle the balance payment.
The goods has been delivered for so long time, how come the balance amount is not paid yet.
这句话在外贸里有点生硬，可以这么说：货发已久，请速付余款，以免影响退税。
The goods has been delivered for xxx days. We need the balance amount to be paid immediately to avoid tax refund loss.
另外一句：
From previous payment record, we can see you have really good reputation.
供你参考，谢谢。
It's been quite a while since we delivered the goods. I was wondering why we haven't received the remaining payment from you?
We can tell from the payment record in the past that you have very good reputation.
可以说：the balance will be paid before delivery.
或者：the last payment will be made before delivery.
或者：the remaining payment will be made before delivery.