Those tools & supplies are a business related expense. Should I now revise my W-2 with my employer so that less is withheld in taxes?
3 of my goats did not have twins this year - they only gave birth to one kid each. That was a huge surprise and disappointment. It reflects a loss of income of roughly $1000. Hell, with as many goats as I raise, I'm happy if I estimate the income from selling them within $4000...
In your case, you very well could revise your
W-4 repeatedly. But, you'd be much better off paying estimated taxes. Paying estimated taxes is generally quite quick and easy (
17 lines, see page 7).
For me, I created an Excel sheet that does all of it for me (well it doesn't put the stamp on the envelope, but it does most of it). You could do it too pretty easilly just using last year's tax form. Then you'll have a line on it that says # of girl and # of boy goats born.
When you pay estimated taxes, you have 5 chances to get your tax right (four roughly quarterly payments, then the final payment when you do your yearly taxes). If you over-estimated or under-estimated on one payment, then you just make up for it on the next payment in a couple of months. That way you can avoid the shock of an $8000 swing in your taxes since you'd be paying $2000 more or less each quarter.
Your case sounds fairly simple. You could do the estimated payments yourself and have the accountant do the final one. It wouldn't cost you anything that way (other than a possible quick mid-year question to your accountant here or there to see if item XYZ can be deducted). These get much harder for people who have wildly varying incomes who can't even realistically estimate their taxes for a week in advance (think daytraders or sales people).