Disclaimer:
Tax questions tend to be complicated and can be very difficult to answer with the limited information on a forum. If you really want to be at the top of your financial game, you need to educate yourself as much as you can on tax matters as they apply to retirement and investments. Start with your last three tax returns and just get a feel for how they work. Then use one of the online programs like Turbo Tax to start running what if scenarios so you can get a feel for what various scenarios do to your tax liability. Read specific IRS rules around applicable retirement accounts. If this sounds like too much, the next best option is to find a tax advisor (doesn't have to be a CPA). This can be equally as difficult as tax knowledge and strategy vary even among the experts (and not so experts). Once you have done this, use the forum to "gut check" a certain strategy. This is where we can really help.
That said, this is the best I can offer:
If you qualify, a traditional IRA or 401(k) contribution would certainly help reduce your current tax liability.
Does the boss currently offer a retirement plan? If not, it would be a great time to start one, as it should significantly increase the amount of income your husband can defer taxes on. It sounds like your husband may be in great position to help steer this process. Have him focus on options that offer low fee index funds such as Vanguard. I am not self employeed or work for a small company but others may be able to help with the best kind of account, options may include 401(k), SEP IRA, Solo 401(k), etc.
A Jan 1, 2015 payment may make it a little easier to plan for next year(plus 2015 limits are higher) vs Dec 31 2014, which is almost over, but it would also depend on you're expected income for next year.
I would not agree to any type of structured payment arrangement past that, there are just too many things that can go wrong in a 1 man shop.
