# What Are Overflow Calls? Handling Call Spikes

Source: https://insertchat.com/glossary/overflow-calls

> Overflow calls are the calls your team can’t pick up because every line is busy. Learn what causes overflow, how overflow answering works, and how to size it.

Overflow calls are incoming calls that arrive when everyone who normally answers is busy or unavailable, so they would otherwise ring out, hit voicemail, or wait on hold. Overflow answering sends those calls to a backup, such as another team, an answering service, or an AI receptionist, so peak times don’t turn into lost customers.

## How overflow call handling works

Overflow is a routing condition, not a different kind of call. The phone system rings your team first; when nobody answers within the ring time, or every line is in use, the call moves to the overflow destination. Conditional forwarding on a carrier line does the same with “no answer” and “busy” rules.

Overflow is predictable. It peaks on Monday mornings, month-end, after storms or heat waves, and whenever a marketing campaign lands. The useful question is not whether overflow happens but what the caller gets when it does: a voicemail greeting, a hold queue, or someone who can actually answer and book.

## Example: a mover at month-end

In the last week of the month, a local moving company gets quote requests faster than two office staff can answer. Calls ring the office for 15 seconds, then overflow to the AI receptionist, which collects move dates, addresses, and home size and books estimate calls into open slots. The office works the list between calls. This scenario is illustrative.

## Overflow answering in InsertChat

Use InsertChat’s “AI when unanswered” routing: every call rings your chosen number for 5 to 60 seconds, then the [AI receptionist](https://insertchat.com/product/after-hours) answers if nobody picks up. Because the assistant handles each call separately, a spike does not create a queue.

Each overflow call lands in the [shared inbox](https://insertchat.com/product/inbox) with a transcript, summary, and contact details, and high-intent alerts flag callers who want to book or get a quote. See the [moving company setup](https://insertchat.com/industries/moving).

## Is overflow the same as after-hours answering?

No. Overflow covers calls during open hours that nobody can take. After-hours answering covers calls when you’re closed. Many businesses use one routing setup for both.

## How do I know how many calls overflow?

Check your phone provider’s missed-call or call-detail report for unanswered calls during open hours. Once an answering system takes them, its conversation log shows how many calls it handled.

## Related terms

- [Call routing](https://insertchat.com/glossary/call-routing): Call routing is the set of rules that decides where an incoming call goes and who answers it.
- [Call abandonment rate](https://insertchat.com/glossary/call-abandonment-rate): Call abandonment rate is the percentage of incoming calls where the caller hangs up before reaching anyone, while ringing, during a phone menu, or on hold.
- [Missed call](https://insertchat.com/glossary/missed-call): A missed call is an incoming call that ends before anyone answers, because nobody picked up, the line was busy, or the caller hung up while ringing or on hold.
- [AI answering service](https://insertchat.com/glossary/ai-answering-service): An AI answering service answers a business’s phone calls with voice AI instead of call center staff.
- [Conditional call forwarding](https://insertchat.com/glossary/conditional-call-forwarding): Conditional call forwarding redirects a call only when a condition is met: nobody answers within a set number of rings, the line is busy, or the phone is off or out of coverage.

## Related InsertChat pages

- [Overflow and after-hours answering](https://insertchat.com/product/after-hours)
- [Shared inbox](https://insertchat.com/product/inbox)
- [AI receptionist for movers](https://insertchat.com/industries/moving)