My husband and I have 2010-2013 taxes to file. He refuses to give me his income information because he believes the federal govt taxing us is unconstitutional. So I just had 4 years of taxes filed (no deductions) based just on my income and taxes withheld and have federal and state refunds amounting to about $7500. However, he refuses to sign the return. If I file Married Filing Separate I will OWE thousands of dollars plus penalties and interest for late filing and late payment. What can I do?
If you filed as married filing jointly and didn't include your husband's income, your reported income was incorrect. The joint return has to include the income from both spouses (see here). If you got a refund, it's likely because your reported income was artificially low (since it didn't include your husband's income).
You can look up the requirements for head of household; basically you would have to live apart from your huband for most of the year and also have a dependent.
It sounds like you are in a rough situation, but I don't think there is an easy solution. If your spouse does not consent to filing jointly, and you're not eligible to file as head of household, you must file separately as long as you remain married to him (unless you obtain a legal "decree of divorce or separate maintenance" as described in Publication 17, linked above).
If your husband believes that income tax is unconstitutional then he's bound to jail. You, on the other hand, are a separate individual making separate decisions.
If you do want to file a tax return and pay your taxes - you'll have to do it on your own, in this situation, as MFS. Yes, it means you'll pay more taxes because your husband is a jerk. No, nothing you can do about it unless he changes his mind.