"Nothing is certain except for death and taxes," goes the old saying attributed to Benjamin Franklin (but very likely coined earlier). It's hard to argue that death won't eventually come to us all, but while taxes are also hard to avoid, the amount of taxes that you pay is not set in stone. There are lots of ways to shrink your tax bill, such as via credits and deductions.

It's worth noting that the Tax Cuts and Jobs Act of 2017 doubled the standard deduction, which means that many people who previously would have itemized their deductions will no longer find that worthwhile, as the standard deduction will save them more. Still, plenty of itemizers will remain. If you're one of them, here are six of the best deductions for trimming your tax tab. Learn more about them and see how many you can take advantage of come tax time.

Image source: Getty Images.

No. 1: Mortgage and home loan interest

Let's start with the deduction for mortgage interest, which allows you to deduct much or all of the interest you pay on your home loan. For many people, this can amount to more than $10,000 annually. The rules changed with the 2017 tax reform legislation, so here's the latest:

• The maximum mortgage size for an allowable deduction is now $750,000, down from $1 million, for loans taken out prior to Dec. 16, 2017.
• Home-equity loan interest is now only deductible if you used the loan to buy, build, or improve your primary or secondary home. If the money went to pay off credit card debt or to buy a new car, you're out of luck.

No. 2: State and local taxes

Up until the 2017 tax year, you could deduct the state and local taxes you paid on your property plus the state and local taxes you paid on either your income or your property during the tax year. All together, it could add up to a hefty sum.

The rules have changed, though, and now your total state-and-local-tax deduction is capped at $10,000. That's a big bummer for those with high-priced properties and/or outsized incomes or spending habits, but other folks will find the deduction welcome, whether it's $1,000 or $10,000.

This deduction does require a bit of work, though, as you (or your tax preparer) will need to determine whether you'll save more by deducting your state and local income or sales taxes paid. The IRS offers a handy calculator to help you.

No. 3: Retirement account contributions

Next up are retirement accounts such as IRAs and 401(k)s, both of which come in traditional and Roth forms. They provide valuable tax breaks, but they're also important just because they can help us build critical nest eggs for retirement.

Traditional IRAs and 401(k)s accept pre-tax contributions -- and give you an up-front tax break, allowing you to deduct the amount contributed, thereby shrinking your taxable income. And the maximum contributions allowed can be rather generous: For the 2019 tax year, you can contribute up to $6,000 to an IRA (or a total of up to $6,000 can be divided among multiple accounts), plus an extra $1,000 for those 50 and older. With 401(k) accounts, in 2019, you can sock away up to $19,000, plus $6,000 for those 50 and older.

If you save and invest effectively in such retirement accounts, you can amass quite a bit. Check out the table below, which reflects an average annual growth rate of 8%:

No. 4: Home-office expenses

Next, if you toil from home much or all of the time, you might be able to deduct a bunch of home-office expenses. There are rules and restrictions, though, of course:

• The office must be used solely for business. You can't count the family den in which you have a desk in the corner.
• The room(s) must also be your principal place of business or where you meet customers regularly. This means that if you work elsewhere most of the time, such as at your employer's offices, and work from home for that job for a day or two per week, the office won't qualify. (It could qualify if you have a part-time business that you work on solely from that room, though.)
• You need to figure out what percentage of your home your office takes up. You can do this by determining the office's square footage and dividing it by the home's total square footage. Or, if your rooms are all roughly similar in size, you might just divide the number of rooms the office takes up by the total number of rooms in the house.

Deductible expenses include electricity, heat, property taxes, home insurance, security expenses, homeowner association fees, repairs, maintenance, and more. As an example, if your home insurance costs $1,500 and your office takes up 10% of the house, you'd deduct 10% of $1,500, or $150. Spend $10,000 for air conditioning for your house? You might be able to deduct $1,000.

Image source: Getty Images.

No. 5: Contributions to health savings accounts

A health savings account (HSA) is a great way to save on healthcare expenses -- and it can even serve as a retirement savings account, too. As with a traditional 401(k), you contribute money to it on a pre-tax basis via your employer. Then you can spend that money on qualifying healthcare expenses, such as prescription drugs, doctor visits, lab work, dental care, braces, surgeries, and more. The money not spent can accumulate in the account -- there's no use-it-or-lose-it condition, as there is with flexible spending accounts (FSAs). Best of all, once you turn 65, any money in the account can be used for any purpose at all -- you just have to treat withdrawals as taxable income.

Note that you'll need to have a qualifying high-deductible health insurance plan if you want to fund an HSA. For 2019, the HSA contribution limit is $3,500 for individuals and $7,000 for families, with those 55 or older able to chip in an additional $1,000.

No. 6: Charitable contributions

Finally, deductions are allowed for charitable contributions, and if you're very generous, Uncle Sam will be generous, too. You can deduct contributions made to qualifying organizations only, and you'll need to keep receipts or acknowledgments from them for your tax records. (If the IRS questions any contribution, you'll need to prove it.)

You can also get a deduction by donating goods, such as clothes you no longer want or furniture you're replacing. Look up the fair market value of items you donate online, perhaps by using Google to look up "donation value guide." If you do some driving for charity, such as delivering meals to homebound people, you may be able to take a deduction for your mileage. The rate for that in 2019 is $0.14 per mile.

The six deductions above are major ones, but there are lots of other tax deductions you could be able to take, some of them substantial. Do yourself a favor and learn more about them to see how much money you might be able to keep in your pocket.