Customers reach your records two ways: entered directly, or synced from a connected field service or accounting system.
Adding one
Open Accounting → Customers and add the customer with their name, contact details and address. Where a field service system is connected, you can add the customer there instead and let it sync — which is usually better, because it avoids the same customer existing twice under slightly different spellings.
Parent customers
A customer can be recorded as belonging to a parent, which is how you handle one client with several sites, properties or subsidiaries.
This matters for risk rather than for billing. Four accounts that are all the same property management company are one relationship, and losing it loses all four — see customer concentration.
Merging duplicates
Duplicates arrive honestly: the same business entered twice, or synced from two systems with different spellings. Merging combines them and keeps the history rather than discarding it.
Worth doing because the effect of a duplicate is not obvious. Revenue splits across two records, so your largest customer looks like two medium ones and concentration reads as safer than it is.
The routine
Review the customer list once a quarter for duplicates and changed names. Ten minutes, and it is the input every customer-level figure in the platform is built on.