However, if you are finding this to be a consistent and long term issue please see a councilor. They can help and diagnose far better than you will find here. If you find that gets put off as well, ask a friend or family member to help you make and keep the initial appointments. You may be surprised by the number of people that are willing to help free of judgement if you will let them.
Hire a tax preparer. It costs more than doing it yourself, but I find we often discount the cognitive cost of just doing a thing when considering whether to outsource stuff.
In other words, build / use systems to minimize the impact of your own limitations on your responsibilities.