SaaS

What is SaaS?#

NIST defines SaaS as a cloud service model in which the consumer uses the provider's applications running on cloud infrastructure and does not manage or control the underlying network, servers, operating systems, storage, or individual application capabilities — with the possible exception of limited user-specific configuration settings. NIST's broader cloud definition adds five essential characteristics: on-demand self-service, broad network access, resource pooling, rapid elasticity, and measured service. (NIST SP 800-145)

That definition is about who operates the software. The commercial arrangement layered on top usually combines:

Salesforce describes its cloud services as letting customers use multi-tenant software without taking possession of it, with cloud-service revenue generally recognised ratably over the contract term. (Salesforce fiscal 2026 Form 10-K) That is one company's accounting policy under its own facts, not a rule you can copy — apply the applicable standards with an accountant.

Why does SaaS matter to founders?#

Recurrence is earned repeatedly. A signed contract creates a billing right; the product has to re-earn the renewal. High switching friction can postpone churn without producing a satisfied customer, which shows up later as a cliff rather than a gentle decline.

Delivery never ends. Hosting, support, security review, compliance evidence, backups, and upgrades run for the whole term. Perpetual-licence software pushes much of that to the customer. SaaS keeps it, which is why the gross-margin line is a business-model question, not an infrastructure detail.

Cash and revenue diverge on purpose. Annual prepayment is a working-capital instrument. It funds growth and creates an obligation to serve. Bookings, billings, cash, ARR, and GAAP revenue answer five different questions and should never be used interchangeably in a board deck.

Small metric errors compound. Churn, discount depth, implementation burden, and cost of revenue all multiply through the lifetime of a cohort. A cohort-level model is far more informative than a single LTV/CAC ratio, which collapses timing, mix, and survivorship into one unfalsifiable number.

How do you model SaaS economics?#

1. Define the service boundary#

Write down what you operate, what the customer configures, the support tier, data responsibilities, integrations, service levels, and the exit process. Every promise has a delivery cost and a risk owner. Ambiguity here is the single most common source of unprofitable enterprise deals.

2. Choose the recurring value unit#

Per seat, per account, per location, per tier, per unit of usage, per workflow, or a hybrid. The unit should be predictable for the buyer, auditable by both parties, and correlated with delivered value. See pricing metric, seat-based pricing, and usage-based pricing.

3. Keep the contract metrics distinct#

If any part of your ARR is usage-based or cancellable, label it. Salesforce, for example, ended fiscal 2026 with $72.4bn of remaining performance obligation against $41.5bn of full-year revenue — a reminder that contracted future revenue and recognised revenue are separate quantities. (Salesforce Q4 FY26 results, 25 Feb 2026)

4. Measure retention two ways#

GRR = (starting recurring revenue − churn − contraction) / starting recurring revenue

NRR = (starting recurring revenue − churn − contraction + expansion) / starting recurring revenue

Both exclude revenue from customers acquired in the period. Report logo retention and revenue concentration alongside them, and state the window — most public companies report NRR on a trailing-twelve-month basis, so a monthly figure is not comparable to it.

5. Measure delivery economics#

gross margin = (revenue − cost of revenue) / revenue

Cost of revenue typically includes hosting, third-party services and models, support and service personnel, payment costs, and other directly attributable delivery cost. The classification policy has to be consistent and disclosed, because moving support between COGS and opex changes gross margin without changing the business.

6. Measure acquisition and payback#

CAC = attributable acquisition spend / new customers

payback months = CAC / monthly gross profit per new customer

This formula quietly assumes the cohort does not churn during the payback window and that no further sales and marketing cost is incurred to keep it. For implementation-heavy products, decide explicitly whether onboarding effort is acquisition investment or cost of revenue — the answer changes both CAC and gross margin.

Worked example#

A SaaS company starts the month with 200 customers paying $500 MRR each — $100,000 starting MRR. During the month churn removes $2,000, contraction removes nothing, expansion adds $5,000, and 20 new customers add $10,000.

GRR = ($100,000 − $2,000) / $100,000 = 98%

NRR = ($100,000 − $2,000 + $5,000) / $100,000 = 103%

Ending MRR = $100,000 − $2,000 + $5,000 + $10,000 = $113,000

NRR excludes the new customers; total MRR growth includes them. Caveat: this is a one-month NRR. Do not present it next to a peer's trailing-twelve-month NRR, and do not compound it — 103% monthly implies 42.6% annual expansion, which is a very different claim.

At 82% gross margin, starting monthly gross profit is $82,000. The company spent $48,000 acquiring the 20 new customers:

CAC = $48,000 / 20 = $2,400

Monthly gross profit per new customer = $500 × 82% = $410

CAC payback = $2,400 / $410 = 5.85 months

Now suppose all 20 prepay $6,000 for a year. The company collects $120,000 of cash but, under a simple ratable-service assumption, recognises $10,000 of subscription revenue per month. Cash collection is not first-month revenue.

Finally, add implementation: each new customer needs $1,500 of unbilled onboarding.

Effective CAC = $2,400 + $1,500 = $3,900

Payback = $3,900 / $410 = 9.5 months

The same cohort is either a 5.9-month or a 9.5-month payback depending on one classification decision. State the policy before you quote the number.

Related concepts#

• Subscription Model — designing recurring access, commitments, and renewals.
• Usage-Based Pricing — adding a metered component when cost tracks consumption.
• Pricing Metric (Value Metric) — choosing the unit you charge for.
• Managed Services — comparing shared software delivery with labour-intensive operations.
• API as a Product — the same economics with a developer-facing surface.
• Cohort Analysis — measuring retention and payback by start group.

Sources#

1. Peter Mell and Timothy Grance, The NIST Definition of Cloud Computing (SP 800-145), National Institute of Standards and Technology, September 2011. Source for the formal SaaS service-model definition and the five essential cloud characteristics.
2. Salesforce, Inc., fiscal 2026 Form 10-K (year ended 31 January 2026), filed 2026. Source for multi-tenant access without possession and ratable recognition of cloud-service revenue.
3. Salesforce, Inc., Salesforce Delivers Record Fourth Quarter Fiscal 2026 Results, 25 February 2026. Source for FY26 revenue of $41.5bn, RPO of $72.4bn, and cRPO of $35.1bn.
4. Snowflake Inc., Snowflake Reports Financial Results for the Fourth Quarter and Full-Year of Fiscal 2026, 25 February 2026. Source for FY26 product revenue, 125% net revenue retention, and 75.8% non-GAAP product gross margin.
5. U.S. Federal Trade Commission, FTC Seeks Public Comment in Response to Advance Notice of Proposed Rulemaking Regarding Negative Option Marketing Practices, 11 March 2026. Source for the reopened negative-option rulemaking following the Eighth Circuit vacatur.
6. Federal Register, Rule Concerning the Use of Prenotification Negative Option Plans (ANPRM), 13 March 2026. Source for the publication date and the 13 April 2026 comment deadline.