Make it right, Peace of Mind is more important
A declaration from an earlier year can be reopened on your own initiative, and based on the correction you are liable to pay: the tax and interest are payable, the surcharge is not.
Not sure whether you missed anything? Try the Expat Focused — Deduction Check — a few questions per topic, nothing stored.
For people who moved here, the missed item is almost always the same kind of thing — an account left open in the previous country, a fund that kept paying dividend, a flat that was sold. None of it appeared in the pre-filled declaration in Sweden. The good news is there is way to correct the past mistake.