Overwhelming Workload😔

I posted a few months back about my colleague quitting. I am a Tax Analyst & my team consisted of 3 people. Since he left the company it was decided that his position didn't need to be filled so they (meaning corporate) decided not to replace him. This was mid September. From December-May maybe late April, our workload is HUGE! January we file municipal taxes(over 1500 filings), February we file state taxes (over 250 filings), March are the first quarter estimates (roughly 60 filings) , April & May are considered cleanup months. This just means amending returns and or submitting final payments. In between these we still have data reporting and our normal accounting responsibilities.

We are now in our busy season and I just can't seem to stay ahead of my work. Not because I can't or don't know the work but simply because it's a lot of work. It doesn't help that my manager can't help process things because she has to do final reviews but also that she relied heavily on my colleague previously, that she knows almost nothing about processing. She made an argument to corporate that it is IMPOSSIBLE for 1 person to do this job. They replied back (in so many words) saying oh well. Figure it out and get it done. So, I've been getting things done. I do my work as flawless as I can but I'm getting tired. It sounds so little but trust me, the workload is not! I'm interrupted from my work all day everyday with requests and demands others need. I ask my manager to step in and she does sometimes other times she tells me to do it, fine I do it but much of this requires research and it's time consuming.

Idk what to do anymore. I finally expressed to my manager that I am feeling extremely overwhelmed. Initially she ignored me and later came to me and said that we're all feeling overwhelmed. My problem with that is, no one else's workload has doubled. Literally except mine. So it's hard to be understanding. I feel like I've been complaining about it and I've asked God to forgive me because I'm truly thankful.

I'm also growing very resentful because those who decided to eliminate us hiring an additional person don't know exactly what we do. They just saw an opportunity to save money.

I'm at a total loss here. I'm pushing through and making it work the best I can but I don't want to go from overwhelmed to completely burned out. I LOVE my job but I'm feeling defeated because I'm use to performing exceptionally well and I feel like my work now is mediocre. I smile through frustrated or not and I get it done.

I know we all face things in our careers.

Any advice?