The Coronavirus Aid, Relief, and Economic Security (CARES) Act that passed in March 2020 allowed businesses to defer paying their employer share of Social Security (OASDI) taxes through the end of that year. This allowed businesses to hold on to a portion of their tax liability to get through any cash-strapped times caused by COVID-19 and basically, have an interest-free loan for a long period of time. The deferred tax would then become due in two equal installments, with half due on December 31, 2021 and the remainder due on December 31, 2022. Here we are at the start of December 2021, and half of that deferred amount is due within the next 30 days.
All businesses that elected to defer their taxes should have received at least one informational notice (CP256V) in the mail in the past months. The IRS even set up a web page with FAQ Answers about the notice and payment of the deferred taxes: https://www.irs.gov/individuals/understanding-your-cp256v-notice
Payments should be made via eftps.gov, but do not wait until the last minute to remit the payment, as it may take a few days to set up your EFTPS online account. Being just one day late on either installment payment can result in the IRS charging a Failure-to-Deposit penalty based on the original 2020 due dates of the deposits for the entire amount deferred. This would be a significant penalty, considering the taxes would immediately be over a year late.
The IRS will issue another courtesy notice sometime in the fall of 2022 as a reminder of the remaining balance due.
If you have the funds now, you may want to remit the entire payment due.