Write a final demand letter for an unpaid invoice

Write a final demand letter to {{customer}} about unpaid invoices, to send by {{delivery_method}}, so that they know exactly what is owed, that this is the last request, and what will happen and when if they do not pay. The letter may later be read by a collections agency, a court or a lawyer, so it must be accurate, calm and complete. This is a draft for us to check, not legal advice.

Unpaid invoices (number, date, due date, amount, any part payments):
"""
{{invoices}}
"""

Reminders already sent (date, method, to whom): {{reminders}}
What the contract or our terms say about payment, late fees or interest, quoted: {{payment_terms}}
The final deadline for payment: {{deadline}}
How they can pay: {{how_to_pay}}
The next step we have decided to take if they do not pay, or "none decided": {{next_step}}
Where we are and where the customer is: {{locations}}
Signed by: {{sender}}

Write the letter with:
1. A heading "Final notice before" followed by the next step, if one is decided, or "Final payment request" if not.
2. One sentence stating the purpose of the letter.
3. A table of the unpaid invoices with the columns Invoice, Date, Due date, Amount, Paid, Balance, and the total due, with the sum shown.
4. The reminders already sent, by date.
5. Late fees or interest, only if our payment terms provide for them, with the rate quoted and the arithmetic shown.
6. The deadline, written as a date, and how to pay.
7. The next step, stated once and plainly, only if we have decided it.
8. An invitation to contact us by the deadline if they dispute any amount or want to agree a payment plan.

For example, the next-step line might read: "If we have not received [total due] by [date], we will [the step we decided]." That example shows the form only; leave the line out if no step is decided.

Keep it under 300 words, not counting the table. The tone should be firm and factual, like a business record rather than an argument.

Rules:
- Do not threaten anything we have not decided to do, such as legal action, credit reporting or publicity, and do not exaggerate the consequences.
- Do not add fees or interest that our terms do not provide for.
- Do not mention anyone's personal circumstances, and do not copy anyone other than the customer.
- If the customer is an individual rather than a business, stop and say that consumer debt collection rules may apply where they live, and that a lawyer should check the letter before it is sent.

If an invoice is missing a due date, or the reminders do not match the invoices, list the gap above the letter instead of filling it in.