Depends on what the bank's policy is.
I think a personal check is good for only ninety days but what will it hurt to ask?

Lori

I worked in a checking account department & am sorry to tell you this, but that check is not good anymore.

Generally speaking, a check becomes "stale dated" after 6 months. However, sometimes there will be an exception noted on the front of the check, such as "Valid for 90 days" or "Valid for 180 days".

You could let your mother know what happened, and perhaps she will re-issue a new check to you.

there is a 180 day limit at my bank.

Thanks everyone. I thought as much. I wouldn't ask my Mom to write a new check. It is my own fault that I forgot about it.
Clare

We had an old check clear the bank and when we questioned bank personnel they said that things like check dates and signatures are not as closely watched as you would think. In other words, it could very well go through depending on whether or not someone notices the date.

I've had very old checks go through, and it wouldn't really hurt you too much to deposit it and see if it clears. Most checks are processed by machines which do not read the dates, although most banks also tell their customers that while they are not required to pay stale dated items, they reserve the right to do so It might come back and depending on the bank they might or might not charge you. That said, it's pretty reasonable to assume that the writer didn't carry it on the books so to speak for all these years so when it clears it'll be a surprise to them and depending on the financial situation it could put them in a bad position such as bouncing other checks and of course the NSF fees are high these days. So it could conceivably hurt them.

If it's an amount you wanted and they're a reasonable person you could mention to them in a humorous way, oh look what I came across!

That reminds me, I used to have "void after 90 days" printed on my checks. Have forgotten to do that lately, although I don't write many checks.

I wouldn't run it through, it would just bring attention to and might cause hard feelings with your mom. If that doesn't matter you can run it through, they don't check the checks to close unless you take it in and want cash. My friend had a check come in with her husband's name on it and he had passed away and his name wasn't on the account anymore. Someone from the bank told her to run it through anyway and it cleared. I ran a state refund through the account with my husband's name on it after he died, the state told me to.

I'm surprised your mother didn't ask you why you hadn't cashed it. Kind of hard to balance a checkbook with a pesky check outstanding every month! I would talk to her before trying to cash it.

Can you ask your mother to write you a new one?