Has your situation changed from last year? That’s the question most tax preparers lead with, and there’s a good reason.

Taxes are dynamic. They’re supposed to grow as you do, rising and falling with your fortunes. Every life has its share of milestones, and many of them throw a wrinkle on your 1040 form. Too often, folks fall asleep on the tax changes, and it can cost them.

“It isn’t always in penalties,” says Bill Brunson, the Internal Revenue Service’s media relations expert. People can miss opportunities, as well. “If you don’t look at your financial situation, and how the tax law affects you for that accounting period, you may be paying too much tax.”

We took Brunson through a hypothetical life, discussing changes that might affect taxes. At each juncture, the IRS has forms, a Web site (www.irs.gov) and a toll-free number, (800) 829-1040, to help you more.

Homesteading!

“When a person buys a home, they pay mortgage interest,” says Brunson. “Generally speaking, the traditional 15- to 30-year mortgage is going to allow (homeowners) to start itemizing beyond their standard deduction”

Good news! But remember: Those nifty homeowner deductions — for car tags, charitable contributions, state income tax and the like — are designed to offset mortgage interest.

“Twenty-nine years down the line, after you’ve basically paid the interest off, you may not be able to itemize,” he says. “That can cause a change in your tax liability, resulting in more tax owed.” See Publication 936.

Bad times!

The tax man can actually have your back if times turn tough.

“Let’s say you’re a single parent, a couple of kids in the house, and you don’t make a lot of money, say $35,000 a year,” he says. “The Earned Income Tax Credit allows individuals to receive money if they file under a particular status.”

Designed to assist struggling families, the EITC can award money above a refund.

“If your yearly income is around $39,000 or less, it can be as much as $4,600. Between 20 percent and 25 percent of the people eligible for this credit neglect to claim it each year,” says Brunson. See Form 1040, Publication 596.

Wedding bells

Newlyweds are prone to a very common mistake. If you married in the previous year — Jan. 1, July 4 or Dec. 31 — you’re married for that year, as far as the IRS is concerned. Couples must change their filing status to married, filing singly or married, filing jointly.

“You want to find which allows you to pay the least tax, of course,” says Brunson. “The only way to know that is to crunch the numbers both ways.”

In a community property state, filing jointly is usually the better deal. And the common mistake?

“When a newly married couple files jointly, sometimes the wife uses her married name without formally changing it.” This will cause a delay, to verify identity. “If you want to use your maiden name, fine,” he says. “But if you use your married name, make sure you change it first with the Social Security Administration.” (www.socialsecurity.gov)

Splitsville!

If you’re divorcing, it isn’t just the children who suffer. Your tax profile takes a hit, too.

“You would look at what your status is at the end of the year,” says Brunson. “So you could be filing as the head of household or single. Divorce could cause you to pay alimony or child support.”

There’s a vast distinction between the two. There is no tax benefit for child support. It is strictly for the benefit of the child. Alimony is a different story. When you pay alimony, and it meets the requirements for alimony, it is a deduction from your return, as well as an inclusion to the recipient’s return. Line 31A on the 1040 form. See Publication 504.

Joe college

Your child may become the big man on campus, but to the IRS, he’s still your little deduction.

“Generally speaking, you can still claim a child as a dependent up until the age of 23, if they are a full-time student. This applies to technical schools, too.” But other deductions are also available to take the edge off education. “You can deduct as much as $4,000 for tuition and fees. And you can claim various credits, like interest paid on student loans. A whole host of deductions depend on the student’s status.” See Publication 970.

Retirement

Retirees, well-schooled in the rhythm of filing returns, sometimes don’t know they can stop.

“These are people who have filed year after year after year,” says Brunson. The minimum taxable amount for married couples, filing jointly, is $16,900. “With an elderly couple that may be higher because of additional exemptions for age and other factors.”

Retirees should revisit “Do You Have to File?” and see if they still need to bother. “If they fall below the statutory requirement, but still submit a return, there’s no refund, no benefit to the taxpayer, but there is a (processing) cost to the government,” he says. “We don’t want those folks to file if there’s no need.” See Form 1040 instructions.

Death of a spouse

Death, along with grief, brings tax adjustments. You’ll have to make some changes to give the IRS some closure:

“Depending on the circumstances, you could be still married filing jointly, or claiming the status of widow or widower. That’s going to give you a better tax benefit than for a single individual,” says Brunson. Survivors must file a final return for the deceased, with specific annotations to mark the death, and they should consult a professional on how this redefines asset ownership. “It depends on how you owned things. Let’s say you both own stock. If you owned it jointly, it’s yours under the rights of survivorship. But you’ll want a ‘stepped-up’ basis on that stock, so when you sell it, you’ll have less taxes on the capital gains.”

Sound confusing? It is! “There are references in the general instructions,” says Brunson. “Or you can call us for help.”

Your little bundle of deduction

“In the year a child is born, you can claim them as a dependent if they meet the dependent requirements,” says Brunson.

As with marriage, if your little bundle beats the Dec. 31 buzzer, you can claim him or her for the preceding tax year, but the child must have a Social Security number to be claimed as a dependent. Adoptive parents should acquire an Adoption Taxpayer Identification Number if their new child has no Social Security number. See Publication 501.