Two questions, two answers
A customer signs on May 20 at $9,000 per month. The invoice for May covers 12 days, so it bills roughly $3,480. That is correct billing.
Their MRR is $9,000 from May 20. That is correct recurring revenue reporting. MRR states the rate under contract, and the rate is $9,000 regardless of which day of the month the contract started.
Booking $3,480 as May MRR creates a problem in June, where the same customer appears to grow to $9,000. Nothing was expanded. The expansion line in the waterfall now holds a number generated by the calendar, and net revenue retention inherits the error.
The snapshot rule
Take MRR as a month-end snapshot. Count every contract active on the last day of the month at its full contracted monthly rate. A contract signed on the 2nd and a contract signed on the 28th both count in full, because both are active on the snapshot date.
The rule has one visible cost. A contract that starts on the 28th contributes almost no cash that month while contributing full MRR, so MRR runs ahead of collections in a heavy end-of-month close. That is a real effect and it is worth reporting. It is not a reason to change the MRR definition, because the alternative moves the distortion into the growth line, where it is much harder to see.
Why end-of-month timing amplifies this
The problem concentrates rather than spreading evenly. ORM's customer data shows the third month of a quarter running stronger than the first two, and Q2 and Q4 running stronger than Q1 and Q3. Deals cluster at period close, which means a disproportionate share of new contracts start in the last days of a month.
A team that prorates first-month MRR therefore books its largest cohort of new customers at their smallest fraction, then reports the correction as growth in the following month. The stronger the quarter, the larger the phantom expansion.
The policy in four lines
Book full contracted MRR from the contract start date. Snapshot at month end. Keep prorated billing in the billings and cash lines where it belongs. Report a separate reconciliation between MRR and cash collected so the timing gap is visible without contaminating the recurring number.
Then hold the definition still. A forecast built on MRR that changes definition between periods will miss for reasons that have nothing to do with the market, and the forecast accuracy review will spend its time arguing about arithmetic instead of about what changed in the business.
Frequently Asked Questions
Should MRR be prorated in the first month?
No, under the standard snapshot approach. MRR describes the monthly rate a customer is contracted to pay. A customer who starts on the 20th is contracted at the full rate from the 20th, so booking a partial amount creates a phantom expansion the following month.
What is the phantom expansion problem?
A customer starting on the 20th is booked at roughly 39 percent of their rate, so month two shows their MRR jumping about two and a half times. The expansion line then reports growth that came from a billing convention rather than from anything the customer bought.
When does prorating MRR make sense?
When you are reconciling MRR to cash collected or to recognized revenue in the same month. Those are different questions from the recurring rate, and they need the partial period. Keep them as separate reported lines rather than overwriting MRR.
What snapshot date should you use?
The last day of the month, applied consistently. A month-end snapshot counts every contract active on that date at its full rate and ignores anything that started and ended within the month, which is rare enough to handle as an exception.
Put these metrics to work
ORM builds custom revenue forecast models that turn concepts like how do you prorate mrr for mid-month starts? into prescriptive action for your team.
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