NEW YORK (CNN/Money) – With two months left in the year, there's still time to trim your tax bill for 2004, or at least keep it from being unnecessarily or unexpectedly high.

Here's a look at some of the changes to the tax law you should be aware of as well as reminders about what hasn't changed but which is worth remembering as the year draws to a close.

Sales-tax deduction: For tax years 2004 and 2005, you have the choice between deducting your state income tax or the sum of your state sales tax if you itemize deductions on your federal return.

The choice is clearest for those residents in states that don't impose an income tax. But for everyone else, it may be useful to crunch the numbers.

For instance, said Cindy Hockenberry of the National Association of Tax Professionals, if you're taking a lot of exemptions and therefore have a very low withholding, it may be that you'll benefit more from taking the sales tax deduction.

Since this change only went into effect in October, it's unlikely you've been diligent about saving your receipts all year. Don't worry. The IRS is creating a sales tax table you can use. On top of that, you're allowed to add the sales tax on vehicles you bought in 2004 and other large purchases.

SUV deduction: If you were planning to buy a large SUV for business and were banking on being able to deduct up to $100,000, think again. First-year deductions for such a purchase are now capped at $25,000 for vehicles bought and put into service after Oct. 22, 2004.

Charitable donation deduction: If you're thinking about donating a car, boat or plane to a charity, the rules will change after this year. Effective Jan. 1, 2005, you will no longer be able to deduct the fair-market value of the vehicle if the charity sells the vehicle. You will only be able to deduct the amount the charity receives from the sale.

In addition, you will no longer be able to deduct non-cash donations over $500 (including a car, boat or plane) unless you've received documentation from the charity indicating whether the property will be sold or used by the organization.

Withholding: If your status changed in 2004 (for instance, you got married or divorced, became a parent or retired), you're holding more than one job, or you have income not subject to withholding (such as rent or capital gains), it's a good time to adjust your witholding if necessary. Make sure you're not having too much or too little withheld from your paycheck.

Tax-loss selling: The rules haven't changed, but they're worth remembering. You can avoid paying tax on your capital gains for the year if you offset those gains with investment losses.

You can use your losses to offset your gains dollar-for-dollar. Beyond that you can use them to offset up to $3,000 of other taxable income. Any losses left over may be carried over to future tax years.

So say you have $10,000 in losses and $5,000 in capital gains. You can use $5,000 of your losses to offset your gains, $3,000 to offset other taxable income, and you can carry over the remaining $2,000.

If you want to take losses on an investment, but still think it's worth owning for the long haul, make sure you observe the wash-sale rule. In order for your loss to qualify as a loss, you may not purchase the same security either 30 days before or 30 days after the sale of your original shares.

Tax-deferred retirement plan contributions: Any contributions you make to a 401(k), 403(b), deductible IRA, SIMPLE IRA or SEP will lower your taxable income for the year.

You can make 2004 contributions to 401(k)s and 403(b)s until Dec. 31. But the deadlines for other plans are more extended.

You have until the due date of your tax return but not later than April 15 to contribute to a deductible IRA. Just be sure to notify the trustee that it is a 2004 contribution.

You have until the extended date of your tax return (which can be as late as Oct. 15, 2005) to make 2004 contributions to a SEP or SIMPLE IRA.

Deducting medical costs: There's no change here. You may deduct unreimbursed medical expenses only if they exceed 7.5 percent of your adjusted gross income.

But if you think you're close to or will exceed the 7.5 percent limit, the authors of PriceWaterhouseCoopers' "Guide to the 2005 Tax Rules" suggest you might consider accelerating and paying for necessary or elective procedures that otherwise would have been done in 2005.

Make maximum use of your flex spending account: If you have a flexible spending plan, you've already set aside earnings tax free to cover unreimbursed medical, dental and vision expenses, thereby lowering your taxable income.

But if you don't incur enough expenses in 2004 to match the amount in your account, you'll lose the money. So make those last-minute appointments, save the receipts for your aspirin and get those prescription sunglasses you've always wanted. For more on which expenses qualify for reimbursement, click here.