Build a Personal Tax Return Workbook: From Source Documents to Refund or Balance Due

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

• Turn a pile of wage slips, bank letters and broker statements into one structured register, measure withholding, catch a document that was entered twice and spot a statement that has not arrived yet.
• Aggregate the cleaned income lines into a category × person grid, check the household totals, measure each partner's share and chart where the income comes from.
• Classify eight broker sales as short- or long-term, net the gains and losses in each group, apply last year's loss carryforward and the annual loss cap, and calculate the loss that rolls into 2027.
• Apply a contribution limit and an interest cap per person, phase out the student-loan deduction as income rises and arrive at each partner's adjusted gross income.
• Calculate the couple's tax twice – each partner separately and both together – with progressive bracket tables and the SUMPRODUCT method, then measure what joint filing saves.
• Count qualifying children with COUNTIFS, reduce the child credit in steps above an income threshold and calculate a childcare credit whose rate falls with income down to a floor.
• Apply non-refundable credits, add the self-employment levy, total withholding and estimated payments, calculate the refund or balance due and flag the quarters that were underpaid.
• Tie every return line back to the document register, cross-foot the income lines against the total, compare with last year and flag the lines a reviewer must look at.