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Short answer: EOM on a medical supply invoice means “end of month”: the payment due date is anchored to the last day of a month instead of counting straight from the invoice date. Software documentation describes at least two different ways to turn an EOM clause into a calendar date, so the same invoice can produce two different due dates. The wording on the quote, purchase order and invoice decides which one applies.
Definition and scope
EOM is a trade and accounting-system convention for payment terms. The contract or purchase-order wording governs. Thomson Reuters’ accounts payable help states that “EOM represents the last day of the current month” and that “EOM+1” represents the last day of the next month; a negative day count means days before the last day of the month.
This page covers how an EOM clause is read when a laboratory, clinic or supply office buys medical or laboratory supplies. It does not cover prices, discounts offered by any particular supplier, or which terms a buyer should accept. For the plain “days from invoice” terms that EOM is often compared with, see Net 30 vs Net 60 vs Net 90 payment terms and Net 30 payment terms.
How the due date is calculated: two documented methods
The two accounting products below handle EOM differently. Both are published help pages; neither is a legal definition, and your supplier’s system may use a third approach.
Method A: month end first, then add days (Thomson Reuters)
For an EOM-based due date, the user “selects the month to use for the calculation, specifies the number of days from that month end, and specifies a Cutoff day.” The cutoff day is “the day after which the due date for payables or receivables will be moved to the following month.” Thomson Reuters’ own example uses EOM, 10 days and a cutoff of 20: a date of March 9 gives a due date of April 10, March 20 also gives April 10, and March 21 moves the due date to May 10.
Method B: add days first, then push to month end (Comarch)
In Comarch ERP Standard, when EOM is selected the due date is the document’s issue date plus the number of days in the Due Date field, then postponed to the last day of that month, then adjusted by the days in the “Correct By” field, which can be positive or negative. When EOM is not selected, the due date is simply the issue date plus the days.
Worked dates (illustrations computed from the rules above)
The dates below are our own arithmetic from the stated rules, for an invoice dated 10 March with a 15-day term. They are not terms from any real supplier.
| Reading of “EOM, 15 days” | Steps | Due date |
|---|---|---|
| Plain days (no EOM) | 10 March + 15 days | 25 March |
| Method B (Comarch, correction 0) | 10 March + 15 days = 25 March, moved to month end | 31 March |
| Method A (Thomson Reuters, EOM + 15 days) | 31 March + 15 days | 15 April |
One invoice, one clause, three dates spanning three weeks. That spread is the reason to settle the reading in writing before the order is placed.
Related terms
- EOM+1, EOM+2: the last day of the next month, or the month after, as the starting point (Thomson Reuters).
- Cutoff day: the day of the month after which the due date moves to the following month (Thomson Reuters).
- Net 30: a day count from a stated date; see Net 30 payment terms.
- Early-payment discounts such as 2/10 net 30: a discount window layered on a due date; see early payment discount 2/10 net 30. Thomson Reuters notes that discount dates can also be EOM-based.
Where it matters for labs and clinics: confirm before ordering
Purchasing and accounts payable staff handle supply invoices under whatever terms the order documents state. A checklist of what to find in writing, drawn from the parameters the two help pages expose:
- Anchor date: invoice date, ship date or receipt date. Both products anchor to the document date; confirm what that date is on the supplier’s invoice.
- EOM or EOM+1: whether counting starts from the current month end or the next.
- Day count and order of operations: days added before the month-end step (Method B) or after it (Method A).
- Cutoff day: whether invoices dated after a certain day roll to the following month.
- Correction days: any positive or negative adjustment to the month-end date.
- Discount window: whether a discount date is counted by days or from month end.
- Where the terms appear: quote, purchase order and invoice should state the same terms; see the vendor onboarding documentation checklist and the invoice processing guide for the surrounding paperwork, and the wholesale medical supply procurement guide for the wider process.
Public institutions: a different clock
US federal contracts are not built on EOM. Under FAR 52.232-25 (Prompt Payment), the due date is the later of receipt of a proper invoice and government acceptance, each starting a 30-day period; a proper invoice must contain the listed items, including invoice date and number, contract reference, itemized quantities and prices, and shipping and payment terms, and a noncompliant invoice is returned within 7 days. That clause applies to federal contracts, not to private purchase orders, so do not assume it carries over to a university or hospital order placed on a supplier’s own terms.
Common misunderstandings
- “EOM means due on the last day of the month.” Not necessarily. Under Method A the last day is only the starting point and days are then added.
- “EOM always means the same thing.” The two documented methods above give different dates for the same inputs.
- “A standard defines EOM.” It is a trade and accounting-system convention, so the contract wording governs.
- “A cutoff day is part of every EOM term.” It is a setting in one product’s payment-term set-up, not a universal element; ask whether the supplier uses one.
FAQ
What does EOM mean on an invoice?
End of month. It ties the due date to the last day of a month; how many days are added and when depends on the stated terms and the system that calculates them.
What is the difference between net 30 EOM and net 30?
Plain net 30 counts 30 days from the stated date. In Comarch’s method, adding EOM takes that result and moves it to the last day of its month; in Thomson Reuters’ method the count starts from the month end instead. Confirm which reading the supplier uses.
Does EOM+1 mean one extra month?
In Thomson Reuters’ documentation it means the last day of next month as the starting point, with any further days counted from there.
Do federal prompt-payment rules use EOM?
FAR 52.232-25 uses a 30-day period starting from invoice receipt or acceptance, not an EOM anchor.
Sources
- Thomson Reuters, “Set up payment terms” (Accounting CS accounts payable help): https://www.thomsonreuters.com/en-us/help/accounting-cs/accounts-payable/set-up-payment-terms (checked 2026-11-01).
- Comarch ERP Standard Knowledge Base, “Due date at the end of the month – EOM”: https://help.comarch.com/standard/?p=419 (checked 2026-11-01).
- FAR 52.232-25 Prompt Payment: https://www.acquisition.gov/far/52.232-25 (checked 2026-11-01).
