You'll need to post a screenie of the monthly totals, as withheld tax is worked out on a month to month basis. If you post just a monthly result for a completed month, then it's easy to work out how much tax will get withheld on the 11th (I think) of the following month so you don't get a nasty surprise.

Also, without showing the dates, I'm just guessing. I assume week C is week 2 of the year, and week D is week 1? So your December deduction was taken out in week 2, then your yearly refund was applied a few days later. Difference between those 2 is 4,783,813, so I assume that was the deduction for December, made on January 11. Tax rate is 30%, so your total profit for December should have between 15,946,040 and 15,946,043. If you go to December, and do total profit + loan payments made + tax deducted, that's the total you should get. Looks about right just eyeballing the numbers you typed in for the previous 3 weeks + week E, there's ~14.7 million profit + ~1.25 mill in loan payments = ~15.95 mill taxable profit.

For any completed month/year, looking at the monthly/yearly income statement, (total profit + loan payments made + tax deducted) x tax rate = tax deducted in the following month.

EVERY other Tax Message I've received (before and since), matched exactly the amount shown as refunded on the income statement.

Not sure what is different here.

Every other time, you've either made a loss in December, so no tax withheld in January, or the January deduction happened in one week, the yearly refund in the next week.