Ask HN: GL Structure for Enterprise Software Startup?

We are an enterprise software company. We have about 50% of our revenues come from professional services, and the other 50% come from software sales. Our client count is very low and will remain low for a long time to come (<10 per year).

We are in the process of putting together some formal structure around our accounting. In particular, we are trying to decide what "cost centers" to include in our GL (general ledger). Our accountant suggested making one for each customer, and by breaking out the costs by "whatever we feel would be useful". However, when we asked for specific examples we got an "it depends" answer.

I would love to know if anyone has any resources they can point us towards to help answer the question. Or, if you can share your own anecdotal advice about particular things you found helpful to have in there.