"Net 30" is a payment term meaning the full invoice amount is due 30 days after a fixed starting point — almost always the invoice's issue date, though not universally. It is the most common default payment term in day-to-day B2B invoicing: common enough that clients will often assume it if an invoice states no term at all, which is exactly why it should be stated explicitly rather than assumed.
The word "net" here means the full amount, with no early-payment discount attached — as opposed to a construct like "2/10 Net 30", which offers 2% off if paid within 10 days but the full ("net") amount by day 30. A bare "Net 30" on an invoice is just the 30-day deadline, nothing more.
What the 30 days count from is the part that causes disputes. The default assumption is the invoice's issue date, but some businesses count from the date the goods or work were delivered instead, and some invoices state terms as "Net 30 EOM" — 30 days from the end of the month the invoice was issued in, which effectively extends the deadline for anything invoiced early in the month. State the starting point on the invoice if there's any chance of ambiguity.
Net 30 sits in the middle of the common range: Net 15 is tighter and suits smaller or newer client relationships; Net 60 and Net 90 are longer terms typically requested by larger clients whose own accounts-payable cycles run monthly or slower. "Due on receipt" is the other end entirely — no grace period at all, payable immediately.
Net 30 is a convention, not a legal default — nothing requires you to offer it, and nothing requires a client to honor it just because it's printed on the invoice. It works because it's familiar and widely expected in B2B billing, which makes it a reasonable default when you have no stronger reason to pick something shorter or longer.
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