Few SQL questions

I'm getting a syntax error

SELECT invoice_due_date,invoice_total,invoice_total/10 as 10%,invoice_total+(invoice_total/10) as plus_10% FROM invoices WHERE invoice_total>=500 AND invoice_total <=1000 ORDER BY invoice_due_date DESC FETCH FIRST 12 ROWS ONLY;

column invoice_number in field list is ambiguous

SELECT invoice_number, invoice_date, payment_date (invoice_total - payment_total - credit_total) as 'balance_due' from invoices, invoice_archive WHERE payment_date IS NOT NULL;

Could I get some help where the errors are?