How a single CRO invoice wrecks your monthly burn picture

A biotech CFO we work with had a problem she could not explain in a board meeting.

For five months, the company’s monthly burn had been steady at $480,000. Then in November, the burn spiked to $1.86 million. Same headcount. Same lab. No new hires, no expansion, nothing in operations had changed. The board wanted to know what happened.

The answer was a single CRO invoice.

CRO stands for contract research organization, the firm that runs your clinical trial in exchange for a contract that’s usually paid in milestones. This particular CRO had sent a $1.4 million invoice covering work performed across four months. The bookkeeper had recorded it the day it arrived. November’s P&L absorbed all of it.

Nothing had actually changed in the business. The cash hadn’t even left yet. But the books made it look like the company had three weeks of runway when in fact they had six months.

This is a common, fixable problem in early-stage biotech bookkeeping. The fix is one accounting concept and a habit.

The accounting concept: accrual

The CFO in our story was running her books on cash basis. That means every transaction got recorded when the money moved. Cash in, cash out. Simple, but for a company with lumpy clinical spend, it produces lies.

The fix is accrual basis. Instead of recording the CRO bill the day it arrives, you record the work as it happens. The CRO did roughly $350,000 of work each month over four months. The books should reflect $350,000 of clinical expense each month, not $1.4 million in November.

This isn’t optional accounting magic. It’s the way every audited biotech runs its books, because investors and auditors both want to see real monthly burn, not invoice timing.

What the picture should have looked like

On accrual basis, monthly burn is a steady $830,000. The November invoice doesn’t distort anything. The board sees the real cost of doing the trial. The CFO can answer the runway question with one number instead of qualifications.

The total spend is identical. Only the timing of recognition is different.

What goes wrong without it

Three things, in this order:

Runway numbers swing wildly month to month, because they’re being calculated off cash burn. The CFO can never tell investors a single confident runway number, because depending on which month you measure, it could be anywhere from four to twelve months.

Board members panic at the wrong things. They see the $1.86M month and start asking whether the company should pause hiring. The CFO has to explain that no, that’s just a CRO invoice, the work was actually steady. By the time everyone calms down, half the board meeting is gone.

The next financing round is harder. Sophisticated investors expect monthly P&Ls done the standard way auditors look for. If you can’t produce one, due diligence takes longer and the valuation gets sharper. Audit-readiness isn’t optional once you cross Series A.

How clinical accruals actually work

For a CRO contract, the bookkeeper needs three things from the CFO each month.

The work plan. What’s the CRO scheduled to deliver this month? Patient enrollment, lab work, monitoring visits, study reports. The CRO contract usually has milestones tied to dollar values. The work plan tells you which milestones are in flight.

A status update. Did the CRO actually do the work? Was a milestone hit? Was a site delayed? This usually comes from the head of clinical operations, not the finance team.

An estimate of the work done. Based on the work plan and the status update, what dollar value of work was performed this month? That number gets booked as a clinical trial expense, with a matching note that says “we owe the research firm this much for work already done.”

When the invoice eventually arrives, you reverse the accrued liability and post the cash payment against it. The expense was already on the books. Only the cash position changes when payment goes out.

The whole process takes maybe two hours a month if the work plan is documented. Without it, you’re just guessing on burn rate.

The same problem with prepaid contracts

Accrual works in the other direction too. If you paid a CRO $600,000 upfront for six months of work, cash basis would show a $600,000 expense in month one and $0 in months two through six. Burn would look terrible the first month and great the rest.

Accrual treats the $600,000 as a prepayment sitting on the balance sheet, then expenses $100,000 a month as the work happens. Monthly burn stays honest.

This is the pattern for any service contract you pay for ahead of time. Research firms, lab supplies bought in bulk, annual software, even some clinical site fees. If the cash and the work happen on different schedules, accrual is the only way to show a real burn picture.

Best practices for early-stage biotech finance

A handful of habits that keep your monthly burn picture honest:

• Run books on accrual basis from day one, even pre-revenue. Switching later is harder than starting right.
• Maintain a documented work plan for every CRO contract. Your bookkeeper needs this to accrue clinical costs accurately each month.
• Reconcile Carta (or whatever cap-table software you use) to the books every month. Stock options, SAFE conversions, warrants, and option exercises all need to tie out.
• Update clinical trial accruals weekly during active enrollment. The work plan changes faster than monthly close cycles.
• Produce a runway report monthly with a stress case at +20% burn. Don’t wait for a board meeting to find out you have three months less than you thought.

Three questions worth asking

If you’re not sure how your books are set up today, ask three things:

1. Are we on cash basis or accrual? If cash, when do we plan to switch?
2. Are clinical trial costs being accrued monthly against a CRO work plan?
3. What does our last six months of monthly burn look like, and would it survive a Series B due diligence review?

If the answers are uncertain, your monthly burn is being driven by invoice timing, not by what the company is actually spending. That is a fixable problem. It also means whatever runway number you’ve been telling the board may not be the real one.

If you want a second pair of eyes on yours, send the last six months of P&L and we’ll tell you whether burn is real or whether it’s an invoice-timing illusion.