I know there is software out there that allows you to create your chart of accounts without assigning numbers. That's great, but it's better to number your accounts with a unique number series.
I have included the "standard" most people adopt for numbering their accounts. If you don't want to get that detailed, you can skip the 7000 series and just have your indirect and general and administrative costs in the 6000 series.
1000 series- Assets
2000 series- Liabilities
3000 series- Equity
4000 series- Revenue
5000 series- Costs
6000 series- Indirect Costs
7000 series- General and Administrative Expenses
So...why bother numbering your accounts? It's easier to organize and understand. If done correctly, account numbers leave the mystery out of classification as descriptions alone can be misleading to a user.
Alright, time to record an invoice for tools and equipment! Wait there's a "Tools and Equipment" account and a "Tools and Equipment Cost"? Which one do I record this invoice to?!
The difference may be obvious to some because it says "Cost" at the end of the second account so you know what's an asset and what's an expense. But imagine if one was 1100 Tools and Equipment and the other 5005 Tools and Equipment Cost. Doesn't that stand out more?!
It should be easier to record journal entries too! Instead of having to wait until the account auto populates after typing in "job costs: m" for material costs, all you'll need to type in is 5002 and the correct account will show up. May seem trivial but that can save you quite a bit of time.
Hope that was helpful!