Choose the right workspace
Select the business that owns the records before opening the customer or catalogue import. Imports belong to that business and do not merge data from other workspaces.
Use the column names shown by the relevant import screen or template. Customer imports and catalogue imports have different fields; a spreadsheet that looks correct to a person may still need its headers adjusted.
Prepare a small UTF-8 CSV
Export the source as CSV and keep it within 64 KB. Start with a few representative records that include the kinds of names, addresses and descriptions your team uses.
Remove rows you do not intend to import. Check email addresses, supported currency codes and price formats. Keep the original file elsewhere so you can refer back to the source if something needs correcting.
Read the preview before committing
Upload the CSV into the preview step. Review the recognised columns and any row-level validation messages. Fix errors in the source file and preview it again.
For catalogue items, check that prices and currencies match the products you sell. For customers, check that the billing name and address appear as you want them to appear when a new document is prepared.
Import once, then inspect
Commit the validated import. A retry of the same import operation is protected against creating the batch twice, but a deliberately new import should still be reviewed for duplicate source records.
Open several imported records and use one in a draft. This confirms the data is useful in the actual workflow, not just accepted by the file parser. Customer and catalogue imports do not import historical invoices or bank transactions.