Tie bar for dishwasher & garbadge disposal breakers

I’ve noticed a very common technique where electricians are tieing two 20 amp breakers togeather with a tie bar but the outlet plug ins are not 220.
One 20 amp breaker has a 12 awg black wire and the other breaker has a 12awg red wire.
They are 110 outlets under the kitchen sink. Could someone explain why they are tiebarred and is there any special wiring inside the outlet box?

This is called a split receptacle .
One half is on the red Phase and the other is on the Black phase .
This breaker is the correct way to do it as Both legs get shut off at the same time .

Multiwire branch circuit, they use a shared neutral. As Roy said it’s very common, especially with dishwasher and garbage disposal.

Helpful safety procedure…

**What does the Code mean when it refers to a multiwire branch circuit?

**A multiwire branch circuit is a branch circuit that consists of two or more ungrounded circuit conductors with a common neutral conductor. There must be a difference of potential (voltage) between the ungrounded conductors and an equal difference of potential (voltage) from each ungrounded conductor to the common neutral conductor [Article 100 Definition, Branch Circuit, Multiwire].

Author’s Comment: Multiwire branch circuits offer the advantage of fewer conductors in a raceway, smaller raceway sizing, and a reduction of material and labor costs. In addition, multiwire branch circuits can reduce circuit voltage drop by as much as 50 percent. However, because of the dangers associated with multiwire branch circuits, the NEC contains additional requirements to ensure a safe installation. See 210.4, 300.13(B), and 408.41 for details.

The double pole was required when the two hot landed on the same yoke. Now they are required for all MWBCs.

As Jim mentioned, just because there is a two pole CB does not mean that there is a MWBC since two circuits on one yoke have the same disconnecting requirement.