How SLA Response Times Work

A service level agreement (SLA) is a contract between a service provider and a customer that defines the expected level of service, typically including uptime guarantees, response times for support requests, and resolution time commitments. Understanding how SLA time calculations work is important before signing: the same "4-hour response" SLA can mean very different things depending on whether the clock runs on business hours or calendar hours.

Business Hours vs Calendar Hours in SLAs

Most SLAs distinguish between priority tiers, and each tier has different time measurement rules.

For lower-priority issues, the SLA clock typically runs on business hours only. A "4-hour response" measured in business hours starting at 4:30 PM on a Friday does not expire until 11:30 AM on Monday. The weekend does not count.

For high-priority or critical issues, especially those involving outages or data loss, the SLA often runs on calendar hours around the clock. A "1-hour response" for a P1 (critical) incident means the vendor is committed to responding within one calendar hour, day or night, weekends included.

When reviewing an SLA, look for the explicit definition of "business hours" and whether it is specific about the vendor's time zone. A US-based vendor's business hours may not overlap with yours if you are operating in Europe or Asia.

Priority Tiers and Their Typical Commitments

SLAs typically define three to five priority levels, each with its own response and resolution windows. A common structure looks like this:

The exact tier definitions and windows vary significantly by vendor and product. This table is illustrative, not universal.

How Response Time Is Measured

The SLA clock typically starts when the ticket is submitted and acknowledged by the vendor's system. Some vendors start the clock only after a human agent reviews the ticket, which can effectively delay the start. Check whether "response" means an automated confirmation email or a substantive reply from a support engineer.

The clock may pause while waiting for information from the customer ("pending customer" status). Most SLA policies exclude this waiting time from the vendor's response clock. If your ticket sits in "pending customer" status because the vendor asked a question, the SLA window is usually paused until you reply.

Uptime SLAs

Uptime commitments are separate from response time commitments and use a different calculation. A 99.9% uptime SLA allows approximately 8.7 hours of downtime per year, or about 43.8 minutes per month. A 99.99% SLA (four nines) allows roughly 52 minutes per year total.

Uptime is typically measured over rolling monthly periods. Downtime is usually defined as the period during which the service is fully unavailable, not degraded. Performance degradation, slow responses, and partial outages may not count against the uptime SLA even if they affect you significantly. Read the definitions carefully.

Remedies for SLA Breaches

When a vendor misses an SLA commitment, the standard remedy is a service credit: a percentage of your monthly fee credited to your account. A typical structure might give you a 10% credit for uptime between 99% and 99.9%, and a 25% credit for anything below 99%.

Service credits are almost always the exclusive remedy in commercial SLAs. The agreement will typically state that service credits are the sole and exclusive remedy for SLA failures, limiting your ability to pursue damages beyond the credit value. If SLA performance is critical to your business, negotiate this clause before signing.

FAQ

Does SLA response time use business hours or calendar hours?

It depends on the SLA. Most standard support SLAs use business hours (Monday through Friday, 9 AM to 5 PM in the vendor's time zone) for non-critical issues. Premium tiers often include 24/7 coverage with calendar-hour commitments. Read the definition of "business hours" in your specific agreement.

What is the difference between response time and resolution time?

Response time is how long the vendor takes to acknowledge a ticket and assign it. Resolution time is how long it takes to fix the underlying problem. SLAs typically commit to both, with shorter windows for response and longer ones for resolution. Meeting the response SLA does not guarantee the issue will be resolved quickly.

What happens if a vendor misses an SLA?

Most SLAs include service credits as the remedy: a percentage of your monthly fee returned if the vendor falls below the committed uptime or response time. Service credits are typically the exclusive remedy, meaning you cannot sue for damages beyond what the credits provide. Check the remedies section of your agreement.