Be honest and transparent - tell them as soon as you know you will not be able to pay on time.
Don’t overshare - unless they ask for a reason, they don’t care.
Have a plan - be sure you tell them what you can do and when you can do it.
If the person to whom you owe money is a friend or personal connection, tell him or her in person or over the phone — not in text. Expect them to react negatively no matter how you deliver the message. This can bring out feelings of betrayal, anger, anxiety. Money is always a sensitive topic.
Pay them back, and when you do, repeat your apology.
Talking Points
Hi <Name>, I’m calling because I’m sorry to tell you that I will not be able to pay you back/ pay the bill by the time we agreed.
You have every right to be angry or disappointed and I’m truly sorry for being unable to meet my commitment.
I’m doing everything I can to correct this mistake and pay your back in full [or with interest] by <date>.
I’m so sorry again for this. Thank you for understanding.