Even one small tweak before year-end can prevent an unpleasant surprise next spring—and keep your cash flow steady heading into 2026.Hit a safe harbor. Rogé recommended paying "90% of this year's tax or 100% of last year's (110% if adjusted gross income (AGI) exceeded $150,000). If you're off track in November, adjust W-4s now so payroll can fix the glide path instead of your April checkbook."Watch special situations. Side gig holders who don't make estimated payments and new retirees who began required min ...