filing back taxes for 2012 and on and using a tax preparer...

they claim that for 2012, processing fees from my credit card processor and mortgage interest cannot be used as they are past statute of limitation of 3 years...

is this true?

NO;NO SOL in claiming mortgage INTEREST ERXPENSES and return processing fee on your late return; There is no years limit to filing back returns.

however,as you can see, in general, you, as a Taxpayer, have until the later of 3 years from the date of the original deadline of the tax return or2 years from the date the tax was actually paid to claim a refund of overpaid taxes from the IRS.
For example, your 2012 tax return is due on April 15th, 2013. Add 3 years to this filing deadline, and you have until April 15th, 2016, to file your 2012 tax return and still get a tax refund. If you file your 2012 return after April 15th, 2016, then your refund expires. It goes away forever because the statute of limitations for claiming a refund has closed.

Thanks for the response...

Your response assumes that a refund is due, what if I owe taxes, would amending the tax filing with additional information reduce tax owed?

or, what if 2012 was filed before 4/15, would it then be possible to amend the filing and get a bigger refund or reduction on amount to pay?

Your response assumes that a refund is due, what if I owe taxes, would amending the tax filing with additional information reduce tax owed?====>>as you can see it depends; so yes or no;say you file 1040X as you forgot to report taxable income on your return, in this case you?d owe more taxes to IRS/ possibly your state; on the contrary, you file 1040X since you forgot to claim deductible expenses or credit or etc, then you may reduce your tax liabilities.

or, what if 2012 was filed before 4/15, would it then be possible to amend the filing and get a bigger refund or reduction on amount to pay?=====>No as mentioned it depends; even if you filed your return before Apr 15th of 2013 for your 2012 return, you are still treated to have filed your return on time on Apr 15 2014,