This is false. The IRS wants you to pay the amount calculated as due under the information they have available about your income.
The IRS is not motivated to collect more income or to deprive taxpayers of refunds. They're motivated to do their jobs, whether that means issuing a notice of amount due, or paying out a refund check (which they do for millions of taxpayers without issue, every year).
If I donate to a charity, it may reduce the tax I have to pay, especially my income is at the boundary between two tax brackets. Would IRS suggest such a donation in order to reduce the tax amount? Tax advisors do that all the time.
That's not how taxes work. Unless you would have donated to a charity anyway in a subsequent year, you never gain money on net from donating since your tax rate is marginal.
Even if you have super low income and you are on the border for benefits (EITC, Medicare), donating to a charity will not make you eligible for those benefits because that eligibility is determined by AGI, which is income before deductions.
The only situation which this makes sense on net is if you tell your tax advisor that you want to donate some amount of money over the next few years. Then the advisor might tell you to donate in high-earning years to offset a higher marginal rate. In the above proposed scheme, the IRS would only get one year's worth of data, so it cannot recommend you this type of tax avoidance.
There are scenarios in tax planning where expert advice can change the tax you owe by getting you to do something slightly different.
If you bunch deductions, you might alternate between the standard deduction and itemizing deductions, meaning if you want to support charities with $10K per year, you're better off to donate in Jan and Dec of the same year (itemizing), then skip 13 months (taking the standard deduction), then donate twice in the year after that (itemizing), etc. With the increased standard deduction, this may be needed to allow your donations to become deductible at all.
There are other planning strategies that a combined advisor and preparer can help with. (Using your HSA optimally as a retirement account. Optimizing your Roth conversions over the years. Modeling whether Backdoor Roth contributions make sense (or "what would you have to believe is true to have them make sense?") For business owners, setting the balance between your salary and distributions of profits.) Those are advice activities that overlap with a detailed understanding of your financial and tax situation and often mean that you have to change something about the structure or timing of your activity to accomplish your goal.
The IRS is in an OK position to look back and judge "based on what actually happened, here's what you owe", but in a terrible position to offer optimization advice.
$10 for the first bracket. The remaining untaxed income is $1, taxed at 90% = $0.90 tax.
But the Republican Party has spent a lot of money to make people think that the tax would be $90.90 (i.e,. a flat rate), which is why so many people are opposed to increasing the tax bracket rates...even though the actual affect is marginal to most people (even those affected).
No, because the IRS is not in the business of advising taxpayers about their spending or earning, only about how to calculate the amount due based on what the taxpayers earned or spent over the previous year.
For example, if you fill out your form by hand and say that you owe X, using the single-filer rates but you're married and should have used the married-filer rates, the IRS will notice your error when they process your return and send you a refund check for the difference.
A tax advisor will advise you to possibly make a donation...if it makes sense to do so (i.e., if you itemize). Because you're specifically paying them a lot of money to minimize the amount of tax that you owe.
The IRS is not motivated to collect more income or to deprive taxpayers of refunds. They're motivated to do their jobs, whether that means issuing a notice of amount due, or paying out a refund check (which they do for millions of taxpayers without issue, every year).