I don't believe you can. Your IRA deposit for a specific term is a contract. Both sides have to honor the terms of that contract for as long as the contract lasts. The kicker here would be if your IRA agreement allowed changes to the terms of the agreement. My guess is that your agreement doesn't read that way. I know ours don't.
That would mean that you would have to wait to enforce those terms until the next renewal of the certificate.
THe good news: by providing the new terms now, you have met the change in terms notification on the renewal.
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The opinions expressed here are personal and do not represent opinions of my employer.