这句话中的billing是什么意思,应该怎么理解?

这句话中的billing是什么意思,应该怎么理解?
考研英语2004年Text 4第八段" to develop a Medicare billing code for hospital-based care,"中的billing 一词应该如何理解.
我用的书中对这句话的翻译是：“为医院护理制定一份医疗保障制度的条例,”
用牛津高阶英语字典8th 查 billing 一词,
1.the position,especially an important one,that sb is advertised or described as having in a show,tec
2.the ant of preparing and sending bills to customers
3.the total amount of business that a company does in a particular period of time
但好像这三个意思都不对,我又查了bill 的动词意思,看是不是ing 形式
bill verb 1.to send sb a bill for sth
2.to advertise or describe sb/sth in a particular way
3.to advertise that sb/sth will do sth
我感觉也不是.
billing 在这句话中是什么意思,应该怎么理解,怎么翻译呢?