I wrote a check three months ago, and the recipient has not deposited it yet. Stopping payment and giving them cash would cost me more than the amount of the check. Is there anything else I can do? I do have a carbon copy of the check.
Contact your bank to determine that bank's policy regarding aging of personal checks. You'll note that many commercial operations issuing checks will have an expiration period printed on the check. For personal checks, it's going to be up to the bank.
You can then notify the recipient of the expected period of expiration. At this point, you'll not have had to place a hold on the check, costing you nothing, and placing the onus on the recipient.
In the US checks become stale after 6 months and banks are no longer required to honor them. Bank may still honor them, you should check your bank's specific policies. Many banks process checks electronically and may not notice that the check is stale when deposited/cashed.
In the US, unclaimed property is managed by States and different States have different rules. Depending on the situation you may or may not be legally required to follow the unclaimed property reporting requirements. Here's example from my State of California:
California law requires corporations, businesses, associations, financial institutions, and insurance companies (referred to as “holders”) to annually report and deliver property to the State Controller’s Office if there has been no activity on the account or contact with the owner for a specified period of time (generally three years).
California law requires all holders (corporations, businesses, associations, financial institutions, and insurance companies) of unclaimed property to attempt to contact owners before reporting their property to the State Controller's Office.
Holders are required to send a notice to the owner’s last known address informing them that the property will be transferred to the State Controller's Office for safekeeping if the owner does not contact them to retrieve it
Check the requirements in your State on how to handle unclaimed property, you may need to deliver the funds to the State on behalf of your recipient.