Why does the buffer depend on fixed costs and not on how much I bill?

Because the buffer's job is narrow: cover what has to be paid out — rent, payroll, insurance premiums — during the stretch before the first reimbursements arrive. Billing volume determines how much money is eventually owed to you (your accounts receivable balance), but it isn't what determines how much cash you need in reserve to survive the wait. Two practices billing very different amounts, with the same fixed costs and the same payment lag, need the same size buffer.

How long does the reimbursement lag actually run?

It varies by payer and claim type, but 30 to 60 days from billing to payment is a common range for many practices, and some payers or claim types run longer. The right number to use is your own actual average, ideally measured from your billing software or clearinghouse reports rather than assumed from a general rule of thumb.

Does this only apply to healthcare and therapy practices?

No — anything billed to a third-party payer on a delay works the same way: healthcare and mental health practices billing insurance are the clearest example, but the same math applies to any business invoicing a slow-paying customer, government contract, or institutional client with a standard 30, 60, or 90-day payment term.

What if I'm already established and just adding a new payer?

The same lag applies to the new payer's billing specifically, even if your existing payer relationships are already flowing steadily. Adding a payer with a longer lag than what you're used to, or a meaningfully larger volume through a new payer, is exactly the kind of change worth resizing the buffer for before it happens, not after.

Cash flow & operations

The Insurance Reimbursement Lag: Why Billed Revenue Isn't Cash Yet

A practice that bills insurance does the work today and gets paid weeks later — a gap that a cash-pay business never has to plan around. The fix isn't complicated, but it has to be sized in advance, not discovered the hard way.

6 min read · Published August 2026

Key Takeaways

Billing insurance means doing the work now and getting paid weeks later — commonly 30 to 60 days, sometimes longer depending on the payer.
Rent, payroll, and other fixed costs don't wait on that lag, which means a practice needs cash on hand to bridge the gap before reimbursements start arriving on a steady rhythm.
The size of the needed buffer depends on fixed costs and the payment lag — not on billing volume, which is a common point of confusion.
Once reimbursements are flowing steadily (billing has been happening for at least one full payment cycle), incoming payments and new billing settle into a rhythm and the buffer stops being drawn down.
This risk is sharpest at launch, when adding a new payer, or after a deliberate push to grow billed volume — any time the billing pipeline is starting fresh or expanding faster than existing reimbursements can keep pace.

The gap that a cash-pay business never has to plan for

A cash-pay business gets paid at the point of service. A practice billing insurance does the work today, submits a claim, and waits — often a month or two — before that revenue shows up as actual cash. The service was fully delivered on day one; the payment doesn’t catch up until much later.

The session happened today. The payment for it is still weeks away.

Why the buffer is about costs, not billing

The number that actually matters isn’t how much you bill — it’s how much you owe while waiting to get paid. Rent is due on the first regardless of when a claim clears. Payroll runs on schedule regardless of the reimbursement pipeline. The cash buffer’s only job is to cover those fixed obligations for as long as it takes the first wave of reimbursements to start arriving.

A practice billing $18,000/month, 45-day average payment lag, $9,000/month fixed costs

Payment lag in months (45 days ÷ 30)1.5 months

Fixed costs during that lag ($9,000 × 1.5)$13,500

Steady-state amount owed to the practice at any time (AR balance)$27,000

Recommended cash buffer before starting$13,500

The $27,000 is what's owed to the practice once billing has been running steadily — a real number, but not the one to size a cash reserve around. The $13,500 buffer is what actually needs to be in the bank to keep paying rent and payroll while that first wave of claims clears.

The buffer only needs to last through one payment cycle

Once billing has been happening steadily for at least one full payment cycle, the rhythm stabilizes: this month’s incoming reimbursements are paying for claims submitted roughly a payment cycle ago, and this month’s new billing becomes next cycle’s incoming cash. The buffer isn’t a permanent cost of doing business — it’s a one-time (or one-time-per-expansion) bridge to get from a standing start to that steady rhythm.

Resize the buffer any time the pipeline restarts

Launching a new practice, adding a payer you haven’t billed before, or meaningfully growing volume through an existing payer all effectively restart part of the pipeline. Each is worth a fresh buffer check rather than assuming the reserve sized for the original launch still covers it.

Where practices actually get caught

The lag itself isn’t the problem — every insurance-billing practice deals with it, and it’s entirely plannable. The problem is discovering the size of it only after fixed costs have already outrun the cash on hand, typically right after launch or right after a deliberate push to grow billed volume faster than reimbursements can keep up. Sizing the buffer in advance, using your own actual average payment lag rather than a guess, turns a predictable timing gap into a non-event instead of a scramble.

Size your own cash buffer

Enter your billed revenue, payment lag, and fixed costs.

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Frequently asked

Questions owners actually ask

Why does the buffer depend on fixed costs and not on how much I bill?: Because the buffer's job is narrow: cover what has to be paid out — rent, payroll, insurance premiums — during the stretch before the first reimbursements arrive. Billing volume determines how much money is eventually owed to you (your accounts receivable balance), but it isn't what determines how much cash you need in reserve to survive the wait. Two practices billing very different amounts, with the same fixed costs and the same payment lag, need the same size buffer.
How long does the reimbursement lag actually run?: It varies by payer and claim type, but 30 to 60 days from billing to payment is a common range for many practices, and some payers or claim types run longer. The right number to use is your own actual average, ideally measured from your billing software or clearinghouse reports rather than assumed from a general rule of thumb.
Does this only apply to healthcare and therapy practices?: No — anything billed to a third-party payer on a delay works the same way: healthcare and mental health practices billing insurance are the clearest example, but the same math applies to any business invoicing a slow-paying customer, government contract, or institutional client with a standard 30, 60, or 90-day payment term.
What if I'm already established and just adding a new payer?: The same lag applies to the new payer's billing specifically, even if your existing payer relationships are already flowing steadily. Adding a payer with a longer lag than what you're used to, or a meaningfully larger volume through a new payer, is exactly the kind of change worth resizing the buffer for before it happens, not after.

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Educational content only. This article is for informational purposes and does not constitute tax, legal, or financial advice. Every situation is different — consult a qualified professional before acting on anything here.