I owe you one.

Meaning

I am grateful for your help and will return the favor in the future.

Examples

• John: 'Thanks for covering my shift.'<br>
• Alice: '<b>I owe you one</b>. Let me know if I can ever return the favor.'
• John: 'No problem, <b>I owe you one</b>.'
• Alice: 'That was incredibly helpful, John.'<br>