The statute of limitations, or time to initiate or bring a lawsuit, in California for promissory notes is 4 years (you use the same statute of limitations as for a written contract). Therefore, you have up to four years from when your ex-boyfriend failed to pay on the note (from what your write, four years from this past March) to sue.If you sue and win and he still does not pay, you can then try to recover the money from him by garnishing his wages, by having court officers levy on (take money from) a bank account, execute on (seize and sell) personal property (such as a vehicle or big screen TV), or put a lien on real estate. Doing these things can be somewhat complex, and will require some work on your part, but there are mechanisms available to you to collect.