Get a Release Letter: Once all obligations are fulfilled, ask for a release letter from the factoring company. This document should state that you have fulfilled all contractual obligations and that the factoring company has no further claim on your invoices or receivables.
Writing--or hiring an attorney to write--a contract cancellation letter is the safest way to go. Even if the contract allows for a verbal termination notice, a notice in writing provides solid evidence of your decision, and it's always a good idea to have a written record.
Leaving Your Current Factor You need to consider the fees associated with switching before committing to the change. Once you've decided to leave your current factor, you will need to give notice. All factoring companies require written notice to terminate the contract.