WASHINGTON — For 2007 income taxes, it's the little things that count. Small deductions here, a credit there, a bit of help for homeowners caught in the mortgage crisis — all add up to tax savings for savvy filers.

But a big thing — Congress' last-minute fix of the alternative minimum tax — delayed filing for several million early birds who usually submit returns months ahead of the April 15 deadline.

Affected were taxpayers claiming any of five credits related to the AMT. This year, they couldn't file before February. More than 13 million taxpayers claim those credits, the Internal Revenue Service said, but only about 3 million to 4 million typically file before Feb. 11, the agency's target date for processing those forms.

For 125 million other taxpayers it's business as usual, the IRS says. And for everyone, including those affected by the five AMT-related forms, tax returns are still due April 15. Tax owed must be paid by that date, even if you file for the automatic six-month extension.

Filing electronically and having your refund electronically deposited into a bank account will get it to you weeks earlier than choosing to receive it by government check.

"We strongly encourage taxpayers to file electronically, particularly those affected by late tax law changes," said Linda Stiff, acting IRS commissioner. "Filing electronically makes things easier by reducing errors and speeding up refunds."

Taxpayers using home tax preparation software should check the companies' Web sites often for updates. Those still grappling with paper forms can print updated forms from the IRS Web site at http://www.irs.gov/formspubs/index.html or order them from the IRS by calling 1-800-829-3676.

Forms also are available at post offices, banks, public libraries and other outlets, though they might not be up to date. But then neither is the tax packet that last year's paper filers received by mail from the IRS in January, because it doesn't include those five AMT-related forms.

SMALL ITEMS ADD UP

When the dust settles, you'll find there's little that's new this filing season, other than the usual inflation-related adjustments. But even small items can add up.

"Make sure that you've got the bases covered. Make sure you know all of the deductions you're entitled to, the credits you can claim," said Maggie Doedtman, client advice manager for H&R Block, the tax preparation giant.

Leading the list of new items for 2007 are tax breaks for homeowners facing foreclosure or struggling with house payments that include mortgage insurance premiums.

Mortgage insurance is required by government and private lenders on home purchases in which the buyer pays less than 20 percent as a down payment. For 2007, taxpayers can deduct mortgage insurance premiums on home acquisition debt that was new or refinanced in 2007. If you simply continued paying premiums on a mortgage that predated 2007, you can't deduct those.

Like many deductions, this one phases out as income rises. Only taxpayers with adjusted gross incomes of $100,000 or less take the full deduction.

Homeowners facing foreclosure have one bright spot, a provision Congress passed late last year as the mortgage crisis took its toll. Taxpayers granted forgiveness of mortgage debt in 2007 don't have to pay taxes on the amount of that forgiveness, up to $2 million ($1 million for a married person filing separately). Previously, loan forgiveness was often taxed as income.

Despite high fuel prices and other energy costs, energy tax breaks are petering out. Homeowners who made certain energy-saving home improvements in 2007 have one last chance to claim the residential energy credit, but only if they didn't use all the credit in 2006. Items that qualify include insulation, certain water heaters, air conditioners, fans, furnaces, skylights, exterior windows and doors, solar panels and metal roofs with pigmented coatings designed to reduce a home's heat gain.

The credit is usually 10 percent of the cost, though there may be separate limits for specific devices. The credit is limited to $500 for the 2006 and 2007 tax years combined.

BREAK ON HYBRID CARS

Taxpayers who bought a new hybrid or alternative-fuel vehicle in 2007 are eligible for the alternative motor vehicle credit, but this phases out beginning in the second calendar quarter after the quarter in which the manufacturer records its 60,000th sale of hybrids and alternative fuel vehicles. Check the IRS Web site for specific manufacturers' models and allowable credits.

There's a new wrinkle in effect for 2007 charitable contributions: tighter record-keeping requirements for smaller cash contributions. Previously, for amounts under $250, a taxpayer's notes or personal check register reflecting the donations was sufficient documentation.

Now, all cash donations must be backed up by official records such as a check, bank copy of the check, electronic funds transfer record, credit card or credit union statement. These must list the charity, donation amount, date paid or transaction posting date. A charity's written acknowledgment showing that information is also OK.

You don't have to submit those records to the IRS, just keep them on hand in case you are audited.

"Everything on the tax form is only as good as the documentation behind it," said Mark Steber, vice president of tax resources at Jackson Hewitt Tax Service, which has 6,000 tax preparation locations across the country. "The IRS is not too forgiving on the 'trust me' phrase."

What are your chances of being audited? Slim, unless you have a high income and large deductions to go with it. That's also the group of taxpayers targeted by the AMT, a parallel tax system designed to make sure the wealthy don't use a lot of deductions to avoid paying their fair share of federal taxes.

However, more and more moderate income taxpayers are ensnared by the tax because it isn't indexed for inflation. In December, Congress spared more than 20 million taxpayers an average extra $2,000 tax hit for 2007 by freezing AMT growth for a year.

Because Congress acted so late, the IRS had to scramble to reprogram its processing system. Since the AMT disallows deductions and credits, it affects a dozen or so tax forms used by many taxpayers, not just by the wealthy.

FORMS REWORKED

The IRS was able to rework most forms quickly. However, the forms for five credits required more significant reprogramming: Form 8863, "Education Credits"; Form 5695, "Energy Credits"; Schedule 2, "Child and Dependent Care Expenses for Form 1040A Filers"; Form 8396, "Mortgage Interest Credit"; and Form 8859, "District of Columbia First-Time Homebuyer Credit."

Two of the credits — the mortgage interest credit and the D.C. homebuyer credit — are used by a relatively small number of taxpayers. And there's a way around Schedule 2 for the child and dependent care credit: Early filers could choose to switch to Form 1040 and attach Form 2441, "Child and Dependent Care Expenses."

The IRS and tax preparation professionals urged taxpayers to start on their returns as soon as W-2 forms arrived in January, even if they couldn't file until the next month.

Tim Gokey, group president of H&R Block retail tax services, said that while taxpayers could go ahead and file a return without the AMT-related forms and amend it later, there were drawbacks to that approach. Amended returns must be mailed to the IRS, and refund checks on amended returns are mailed as well — a process that takes six to eight weeks.

Taxpayers are better off waiting until the forms were finalized, then e-filing the complete return, Gokey said. A refund on an e-filed return comes in eight to 10 days if the taxpayer has IRS deposit the money directly into a bank account.