Almost every invoice that sits unpaid has one thing in common: nobody wrote down when it was due. The seller assumes «soon». The buyer assumes «whenever». And the thirty, sixty or ninety days of waiting live in the gap between those two assumptions.
What almost nobody knows is that the gap isn't empty. If you don't set the date, your country's law already set one. And in several countries that date is a lot sooner than the client thinks.
Silence doesn't mean «whenever you can»
When an invoice doesn't say when it is due, it isn't left to the buyer's judgment. Nearly every commercial code carries a default term: the one that applies precisely because the parties agreed on nothing. It ranges from ten days in Mexico to forty-five in Colombia. None of them says «whenever the client can».
This matters for a practical reason. The day the invoice falls due is the day interest starts running and the day you can start demanding payment. With no date, that clock starts late or never starts. With a date, it starts on its own.
Mexico: ten days, and there is no grace period
Mexico's Commercial Code has the shortest term on this list. Article 83 provides that «obligations that have no term set by the parties or by the provisions of this Code shall be enforceable ten days after they are contracted». Ten days, not thirty.
Article 84 adds something worth having handy in an awkward conversation: «in commercial contracts no terms of grace or courtesy shall be recognized». Article 85 sets when default begins: the day after the due date when there is a fixed date, and from the day the creditor demands payment in every other case.
Read that backwards: with no fixed date on the invoice, default doesn't run by itself. It runs from the moment you chase the client.
Chile: thirty calendar days, and a different term has to be registered
Chile is the strictest case in the region. Since Law 21.131, the balance of an invoice must be paid within a maximum of thirty calendar days counted from receipt. Not from when the client approves it, or books it: from when they receive it.
A longer term can be agreed, but under conditions few people meet by accident. According to the official guide of the National Congress Library, the agreement must be in writing, signed by both parties, not abusive toward the creditor, and registered within five business days with a Ministry of Economy registry. It is also banned when a small company sells to a larger one, unless the extension benefits the smaller firm.
If the client goes past the deadline, the law adds two things: the current interest rate for non-adjustable operations in national currency, and a fixed recovery commission of 1% of the outstanding balance.
Colombia: forty-five calendar days, non-extendable
Law 2024 of 2020, the fair payment terms law, set a stepped ceiling: a maximum of 60 calendar days during the first year of application and, from the second year on, a maximum of 45 calendar days, non-extendable. The count starts from receipt of the goods or completion of the services.
Two caveats: transactions between large companies are excluded — the rule protects micro, small and medium firms — and health system transactions have their own permanent 60-day limit. If you sell alone, you are squarely inside the group the law meant to cover.
European Union and Spain: thirty by default, sixty as the ceiling
The Late Payment Directive 2011/7/EU gives thirty calendar days from receipt of the invoice when the contract sets no date, and bars an agreed term from exceeding sixty calendar days unless expressly agreed and not grossly unfair to the creditor. Spain's Law 3/2004 mirrors it and adds a detail that gets missed: the invoice must be sent within fifteen days of delivery.
The heaviest part is the interest. The directive defines it as the European Central Bank reference rate plus eight percentage points, recalculated every six months. The Spanish Treasury's Resolution of 30 June 2026 set it at 10.40% for the second half of 2026, starting from an ECB rate of 2.40%.
And there is an extra almost nobody claims: at least 40 euros in fixed compensation for recovery costs, automatic, with no reminder required first. Contractually excluding the right to charge interest is always deemed grossly unfair.
United States: thirty days, and seven to send a bad invoice back
In federal government contracts, 5 CFR 1315.4 sets thirty days from the start of the payment period when no other date is agreed. It also protects the vendor with a mirror deadline: if the invoice is improper, the agency must return it «no later than 7 days after receipt», stating what is missing.
Late payment interest is published by the Treasury every six months. For July 1 through December 31, 2026 it is 4.75%. There is no equivalent federal mandate for the private sector: there, your contract and your state's law decide.
Brazil: the duplicata runs on its own clock
Law 5,474/1968 puts deadlines on the document, not just on the payment: the duplicata must be sent to the buyer within thirty days of issue, and the buyer has ten days to return it signed or with the reason for refusal.
Interest changed recently and plenty of people still quote the old 1% per month. Law 14,905/2024 rewrote article 406 of the Civil Code: when interest wasn't agreed, the legal rate is the Selic minus the monetary adjustment index, which defaults to the IPCA. If the result is negative, it counts as zero.
What to do with this on Monday morning
None of the above helps if the invoice goes out with no date. Four concrete changes, each a one-minute job:
- Write the due date, not the term. «Due September 30, 2026» isn't arguable; «Net 30» is, because someone has to work out when those thirty days started.
- Say what the count starts from. Delivery, invoice receipt and service completion are three different dates, and the laws above don't pick the same one.
- Put the late interest in writing. If you don't agree on it, your country's default applies, and it may be lower than what you would have charged.
- Send the invoice fast. Spain gives fifteen days to send it; Brazil, thirty to forward the duplicata. The collection clock doesn't start until the paperwork arrives.
A default term is a safety net, not a plan. When you set the date, the due date is yours; when you don't, it belongs to the legislator, and the legislator doesn't know your cash flow.
This is general information, not legal or tax advice. Rules change and their application depends on the contract and the country. Check with a professional in your jurisdiction.