Hello @BB Hardware,

The error message prompt happens when you edit the default template in sending your customer's statements. Instead, let's manually create a new template so you can add their name on the SUBJECT field.

1. Go to Edit.
2. Select Preferences.
3. Click Send Forms.
4. Go to the Company Preferences tab.
5. Under Email Templates, select Statements.
6. Click Add template.
7. Enter your customer's name in the SUBJECT field.
8. Select Save.
9. Click OK.

I've got you our Help articles in case you need some reference especially with recording your daily transactions.

You can always get back to here in the Community if you have any other questions.