HMRC deleted my tax returns and sent me fines.

So yesterday I received 4 letters for each of the last 4 tax years saying I owe thousands in penalties as I have failed to submit my tax return for those 4 years on time.

I have always submitted it on time and paid on time, this last year I did so with a payment plan, with my final payment being in 7 days.

I log in to my tax account and all my tax returns have vanished and it's telling me I must submit a tax return for each of the last 4 years. Has anyone ever seen or experienced anything like this?

I have copies of all my tax returns, and payments and so does my accountant. I am planning on calling them on Monday, but this doesn't seem like a mistake especially with the timing.