When it comes to official business documentation (USA) between a company and a client who is either another company (B2B) or individual person (B2C), how can the company providing the invoices, prove that those invoices are really not yet paid?

Passed due date is obviously insufficient proof. Also payer's (client's) bank account statement, with missing relevant line(s), is insufficient as well because the payer could have paid with a different bank account.

What else could be done here? Is there any official definition of such USA document and where could I get it?

3 Answers 3


You can't prove a negative.

Therefore, you cannot prove that an invoice is unpaid; it is assumed to be unpaid on claiming so, and the payer has to prove that he paid. That should be easy for him, if they did pay.

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    Hence, why you, as payer, need to ask for receipts, cancellation of the invoice (e.g. a "paid" stamp) or retain proof of payment (cancelled checks or bank transaction statements).
    – pboss3010
    Oct 7, 2019 at 12:25
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    +1, however you could theoretically prove the negative here. For example, production of a contract that states payment must be made to a particular bank account, and bank statements showing that no such payment was ever received there.
    – JBentley
    Oct 8, 2019 at 1:47
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    Seriously, could you please edit or remove the title? Especially with "obviously", since, well, it is wrong. Oct 8, 2019 at 16:40
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    @Mołot the linked article explains it better than I could. "you can't prove a negative" is itself a negative, so how would you prove it if it's indeed true? You're right, the content and explanation are perfectly correct. I just don't think that false claims should be written in bold letters. Oct 8, 2019 at 17:50
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    -1 just for "Obviously, you can't prove a negative." That's misleading and perpetuates a common myth, even if it is the case you cannot prove the non-existence of payment in this case. "It's not hot" is easy to prove with a thermometer reading, "it's not past 5:00" is easy to prove with a clock, etc. Non-existence can be substantially harder to prove than negative statements in general, but is still possible with certain constraints. Almost any negative statement can be rephrased as a positive: "prove it was not paid" == "prove it is still unpaid", but that doesn't mean nothing is provable. Oct 8, 2019 at 18:32

You don't need proof. If you believe someone owes you, just bill them for whatever you think is owed.

The burden of proof is on them to show they paid. On the off-chance they have, any competent business will have no trouble showing this.

However, that should not be happening. Sometimes, that is a routine issue that is easily explained, like paper bills and paper checks crossing in the mail. If you are encountering this situation in other cases, then there is a serious problem with your bookkeeping system. Your own business records are not in order. You need to get them in order before you bill anyone else. Otherwise you will make a fool of yourself with your clients, and accounting departments will become reluctant to pay any of your bills.

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    Is the word "dun" one that any business owner should recognise? I am not, and I do not. Just wondering whether this requires clarification.
    – Tom W
    Oct 8, 2019 at 10:45
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    @TomW I understand what "dun" means in the context, but it is certainly not a word I would use myself. I suspect it may be regional. (See merriam-webster.com/dictionary/dun entry 3, meaning 1.) Oct 8, 2019 at 14:07
  • @TomW okay. . . . Oct 8, 2019 at 18:16
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    @Harper - missed an opportunity there. Ok, I'm dun now.
    – Mazura
    Oct 8, 2019 at 21:03
  • Here is my bill to @Harper for 1 million (what ever) now prove you don't owe me... This answer is wrong, the proposed debtor has no obligation to prove they do not owe money. On the other hand if the debt was due, and both parties agree it was due, the debtor should be able to show it was paid. Oct 9, 2019 at 14:22

If the client is not willing to cooperate, which I'm assuming is the case, there is no way to prove it definitively. Any sane authority should agree that the burden of proof rests on the client to prove that it has been paid. If the client is unable to produce such proof, he is generally judged as not having paid.

Also payer's (client's) bank account statement, with missing relevant line(s), is insufficient as well because the payer could have paid with a different bank account.

And he could have also paid you cash, so even all their statements will be insufficient. However, you could produce your own statement in all accounts in which you receive payment, to show that no payment has been received by you.

Another way would be to get the client to confirm on record that they have not paid.

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    Of course, you don't need to prove it definitively, just "on the balance of probabilites" (that is, it is more likely that the client has not paid than that the client has paid). Oct 8, 2019 at 14:08
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    RE "Any sane authority should agree that the burden of proof rests on the client to prove that it has been paid." I actually have a bit of problem with this in that I think there is also at least equally as much responsibility to prove that the goods, service or whatever is being paid for has actually been delivered or completed. Oct 8, 2019 at 19:37
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    @R.Hamilton Sure, and that's a defense the client is welcome to raise. Oct 8, 2019 at 23:03

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