Net 30 vs Net 15: What Shorter Payment Terms Are Worth

Net 30 means the invoice is due 30 days after its date; net 15 means 15 days. The shorter term sounds like a simple improvement, but the benefit is easy to overstate. Shortening terms does not add 15 days of income to every month. It releases a block of cash once, and after that your monthly receipts look the same as before. Whether that one-time block is worth the friction with customers is a cash-flow and contribution question you can answer with a few lines of arithmetic.

What the term does to the money you are owed

A business with steady sales has, at any time, about as much money owed to it as it sells per day multiplied by the days customers take to pay. Take a hypothetical supplier invoicing $9,000 per month, or $300 per day. If every customer paid exactly on the due date, net 30 leaves about $300 × 30 = $9,000 outstanding at any time, and net 15 leaves about $300 × 15 = $4,500. Moving to net 15 releases $4,500. It arrives as a bump during the changeover month, when invoices on old and new terms are collected together, and then the monthly rhythm returns to $9,000 per month.

Customers do not pay on the due date

The days that matter are the days customers actually take, which equal the term plus lateness. If your customers pay about 8 days late on average, net 30 becomes 38 days and the balance outstanding is $300 × 38 = $11,400; net 15 becomes 23 days and $6,900. The cash released is still $4,500, because lateness is the same in both cases. If instead a shorter term teaches customers to pay faster, or lateness grows because the customer feels the term is unfair, the gain changes. Measure your real collection days from the last six months of invoices before deciding. The days-sales-outstanding guide on this site shows how.

What the released cash is worth

Cash in hand is worth what it saves or earns. Suppose you currently cover short gaps with a credit line and would use the $4,500 to avoid borrowing at an assumed 12% annual rate. The monthly saving is $4,500 × 12% ÷ 12 = $45. Use your own rate; the 12% is a placeholder, not a market figure. The saving is small relative to the business's sales, and it is the benchmark the customer reaction has to beat.

What losing a customer costs

Suppose your contribution margin, the share of each sale left after variable costs, is 40%. The $9,000 of monthly billings then contribute $3,600. The carrying saving of $45 equals 1.25% of that contribution ($45 ÷ $3,600). If tighter terms cause you to lose a customer who accounts for $1,500 of billings per month, you lose $600 of monthly contribution, more than thirteen times the saving. The break-even is stark: losing about 1.25% of your contribution erases the benefit of the faster cash. Short terms are worth it when the money is genuinely scarce, when the customer was paying late anyway, or when you are replacing a loan with a high rate. They are not worth it when your customers have an easy alternative.

The last row is $45 ÷ 40% = $112.50 of billings per month, which is the same 1.25% of $9,000 seen from the sales side. Losing one customer who buys $113 a month is enough to cancel the benefit; losing one who buys $1,500 turns it into a loss.

Discounts are a different tool

A discount for early payment is a separate offer on top of the term. The common notation 2/10 net 30 means a 2% discount if paid within 10 days, otherwise the full amount in 30 days. Financial-management textbooks annualize the cost of skipping that discount with the formula 360 ÷ (30 − 10) × 2% ÷ 98%, which gives about 36.7%. For the seller, the same arithmetic says the discount is an expensive way to raise cash, while a plain net 15 costs nothing per invoice and asks nothing of the customer except a shorter wait. The two choices are covered in more depth in the early-payment discount guide.

Ways to shorten collection without shortening the term

Terms are only one of the levers. Invoicing on the day the work is delivered rather than at month-end, sending a reminder before the due date, collecting a deposit up front, and splitting a large project into milestones all move cash earlier. Each is a cheaper conversation with the customer than a blanket policy change. Make sure the clock is stated clearly: 30 days from the invoice date, from delivery, or from receipt are three different deadlines.

1. Measure actual collection days

   Average the days from invoice date to payment over recent invoices, by customer group.

2. Compute the cash released

   Daily sales times the number of days the term shortens. This is a one-time amount.

3. Price the benefit

   Multiply by your real cost of short-term cash, or the interest you would pay otherwise.

4. Set the loss threshold

   Divide the monthly benefit by your contribution margin to see how many lost billings cancel it.

Method references: OpenStax Principles of Finance: What is trade credit? for the terms notation, the $10,500 invoice example and the annualized cost formula, and OpenStax: What is working capital?. Checked November 3, 2026. Sales, lateness, contribution margin and the 12% rate are hypothetical.