I wear a coat and tie every Sunday for Mass. However, I will often go to Confession either Saturday evening or some other day of the week in the evening, when it is convenient. I typically do no dress up when I go to Confession, and wear my street clothes, which are not immodest, but are not my "Sunday best." This past Saturday, someone came up to me and stated that I should wear a coat and tie anytime I enter a Catholic Church, even if just for a few minutes for Confession or private prayer.
Is this correct?
No, it is not.
In fact, weekday Masses are for workmen. You can appear in your various uniforms without scruple, because it's a workday and not Sunday ("Domingo", which means "[the day] belonging to the Lord")
Better to appear at Mass in your air conditioning repair shirt/slacks or mechanic's overalls than to not attend Mass on a given Monday or Wednesday. God knows that we have to work during the week, that's why he gave us those 6 weekdays between Sundays.
As for the suit coat, that is not required either. Out of respect for God we should A) dress modestly and B) get out our best clothes for Mass.
If the Restoration of the Church occurred, and you were about to meet the new Pope who consecrated Russia
to the Immaculate Heart of Mary, abolished Vatican II, brought back the Tridentine Mass, etc. (in other words, a saint) what would you get out of your wardrobe? That is what you should be putting on every Sunday to meet God
-- if that is indeed what you believe you're doing on Sunday.
But what that "best" consists of is obviously a cultural thing. Do you think the early Christians went to Mass in suit jacket and tie? Give me a break.
In the south (Texas for example) people "dress up" differently than they do in New York. That's fine.