Beginning with 2018, you have until the due date of your tax return, including extensions, to come up with the money and complete a rollover of the offset distribution to a qualified retirement account. (Prior to 2018 the rollover had to be completed within 60 days of the offset distribution) That account can be the 401(k) of the new employer, if the plan will accept the rollover, or to an IRA. Since the offset distribution occurred in September 2019 and will be reported with code M on the 2019 Form 1099-R (along with code 1 if you were under age 55 in 2019 or code 2 if you were otherwise under age 59½), you have until October 15, 2020 to complete the rollover (assuming that you request a filing extension for your 2019 tax return).
