In finance and accounting, acceleration means making a payment or obligation become due earlier than originally planned.

It usually happens when:

A borrower fails to meet loan terms

There is a default in payment

A contract includes an acceleration clause

For example, if a loan has an acceleration clause and the borrower misses an instalment, the lender can demand full repayment immediately.

In simple terms, acceleration means moving up the due date and demanding payment earlier than expected.