Invoice Aging Calculator
Paste open invoices with dates and amounts to get a full aging summary (current, 1–30, 31–60, 61–90, 90+) plus weighted DSO and a flag on the balances most likely to go uncollected.
How do I calculate accounts receivable aging and DSO?
Aging groups every open invoice by how many days have passed since its issue or due date, conventionally into current, 1–30, 31–60, 61–90, and 90-plus buckets. Days sales outstanding is average accounts receivable divided by revenue for the period, multiplied by the number of days in that period. The two measures answer different questions. DSO tells you how long collection takes on average, while aging tells you where the specific risk is concentrated, and a single very old invoice can be invisible in a healthy DSO.
How to use this tool
- 1
Paste your open invoices
One per row: customer, invoice date, and amount outstanding: straight from your AR export.
- 2
Set the as-of date
Defaults to today. Change it to reconcile against a prior month-end close.
- 3
Read the risk concentration
See balances by bucket, weighted DSO, and which customers hold the oldest exposure.
The average hides the risk
A healthy overall DSO can coexist with a serious collection problem. Four patterns that a summary number conceals.
Concentration in the tail
Ninety percent of receivables current and ten percent past 90 days can produce a perfectly respectable DSO. That ten percent is where the write-offs come from, and it is precisely what the average smooths away.
Customer concentration
One customer holding 40% of your open receivables is a different risk profile from forty customers holding 1% each, even with identical aging. Aging by bucket alone never surfaces this.
Disputed vs slow
An invoice unpaid because the customer disputes it needs a different intervention from one unpaid because their payables run on 60-day cycles. Both age identically on the report and only one is a collections problem.
Terms versus behaviour
A customer on net-60 terms at 55 days is current. A customer on net-15 terms at 40 days is seriously late. Aging from invoice date rather than due date makes these two look similar, and treating them the same wastes the collections effort.
Numbers to sanity-check against
These are general commercial conventions rather than audited benchmarks. Acceptable ranges vary widely by industry, customer type, and whether you sell to enterprises with formal payables cycles.
From aging report to collected cash
This shows you where the exposure sits today. Converting that into collected cash means knowing which customers historically pay late but always pay, which disputes are genuine, how each account's behaviour has changed over the last four quarters, and how the resulting timing feeds your cash forecast. That analysis requires joining AR to payment history and customer context, and it needs redoing every week, because the picture changes every week.
See how DataWyse answers thisQuestions finance teams ask about this tool
What is a good DSO?
Within roughly 10 to 15 days of your stated payment terms. A company on net-30 terms with a DSO of 38 is collecting reasonably well. The absolute number matters far less than the gap to terms and the direction of travel over the last several months.
Should aging start from invoice date or due date?
Due date, if your customers are on different terms. Aging from invoice date makes a net-60 customer look delinquent and a net-15 customer look acceptable when the opposite is true. Aging from invoice date is only safe when every customer sits on identical terms.
When should a receivable be written off?
Policy varies, but many businesses provision progressively as invoices age past 90 days and write off once collection efforts are formally exhausted. The important thing is applying a consistent policy rather than deciding case by case, which tends to delay recognition of losses already incurred.
How do I reduce DSO?
Invoice immediately and accurately, since disputes usually start with an invoice error. Set clear terms and enforce them. Contact accounts before the due date rather than after. Most DSO improvement comes from process discipline upstream, not from chasing harder once an invoice is already late.
What is weighted DSO?
A calculation that weights each outstanding balance by how long it has been outstanding, rather than treating all open receivables equally. It responds faster to deterioration in the aged tail than the standard formula does, which makes it a better early warning signal.
Is this tool really free?
Yes. No signup, no email required, no usage limit. It runs entirely in your browser: nothing you type is uploaded to a server or stored anywhere. We build these because the people who find them useful are the people who eventually need a financial analyst that works the same way.
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