SkillMedev Budget Builder
A budget is not a restriction on spending - it is a spending plan made in advance. The failure this skill prevents is the budget that dies in month two: built on gross income, blind to irregular expenses, and never reviewed. Build one that survives contact with real life.
Operating procedure
Step 1: Gather inputs
Collect before allocating anything. Label guesses as guesses.
- Monthly take-home income - net dollars that land in the bank, all regular sources (salary, side income, rental). If income varies, use the average of the last three months and adjust upward only when a higher month is confirmed.
- Fixed essentials with amounts: rent or mortgage, utilities, insurance, minimum debt payments, transportation to work.
- Variable essentials: groceries, fuel, medical. Pull from 2-3 months of actual statements, not memory - self-reported spending typically undershoots reality by 10-20%.
- Wants: dining out, subscriptions, hobbies, entertainment. Statements again, not memory.
- Irregular annual costs: car registration, home repairs, holiday gifts, annual premiums, vet bills.
- Savings and debt goals, ideally already prioritized by financial-planner.
Step 2: Apply the 50/30/20 starting split
Allocate net income across three buckets as a starting point, not a rule:
- 50% needs: rent or mortgage, utilities, groceries, minimum debt payments, insurance, work transportation.
- 30% wants: dining out, subscriptions, hobbies, entertainment.
- 20% savings and extra debt payoff: emergency fund, retirement contributions, accelerated debt payments.
Adaptation rules, in order:
- Needs above 50% (common in high cost-of-living areas, often 60%+): compress wants first, then savings temporarily, until income grows. Never zero out savings entirely - hold at least 5% or the budget has no shock absorber.
- Needs above 70%: this is a structural problem, not a category problem. The fix is income or a housing/transportation change, not tighter grocery discipline. Say so.
- Carrying debt above 7-8% APR: the 20% bucket goes to extra debt payments per debt-payoff-planner, after the starter emergency fund per emergency-fund-planner.
Step 3: Convert irregular expenses to sinking funds
Annual and irregular costs destroy budgets when they arrive unplanned. Divide each predictable irregular expense by 12 and enter that amount as a fixed monthly line item. A $600 car registration is a $50/month line, every month, in a separate labeled bucket.
Step 4: Balance to zero
Subtract every planned expense from take-home income until the result is exactly zero - every dollar gets a job. Money left over gets assigned explicitly: savings, a sinking fund, or extra debt payoff. If spending exceeds income, cut in this order: discretionary subscriptions, then other wants, then savings rate, then needs (which usually means a structural change per Step 2).
Step 5: Set the review cadence
Review at the end of each month before the next begins: compare actual to planned by category. A budget that is never reviewed is a wish list. A category off by more than 15% for two consecutive months is mis-sized - change the budget number to match reality and rebalance, rather than resolving to "do better."
Template
Copy and fill. Percentages are of take-home income.
MONTHLY BUDGET - [FILL: month/year]
Take-home income: $[FILL]
NEEDS (target ≤50%, actual [FILL]%)
Rent / mortgage $[FILL]
Utilities $[FILL]
Groceries $[FILL]
Insurance $[FILL]
Minimum debt payments $[FILL]
Transportation $[FILL]
WANTS (target ≤30%, actual [FILL]%)
Dining out $[FILL]
Subscriptions $[FILL]
[FILL: hobby/entertainment lines] $[FILL]
SINKING FUNDS (annual cost ÷ 12)
[FILL: e.g. car registration] $[FILL]
[FILL: e.g. holiday gifts] $[FILL]
SAVINGS + EXTRA DEBT (target 20%, actual [FILL]%)
Emergency fund $[FILL]
Retirement $[FILL]
Extra debt payment $[FILL]
REMAINDER (must equal $0): $[FILL]
Worked example
Take-home $4,200/mo. Needs total $2,400 (57%): rent $1,450, utilities $180, groceries $420, insurance $150, debt minimums $120, transit $80. Sinking funds $105: registration $25, gifts $50, vet $30. That leaves $1,695. At 57% needs, apply the adaptation rule: compress wants to ~25% ($1,050 - dining $350, subscriptions $60, everything else $640) and put $645 (15%) to savings - $400 emergency fund, $245 extra on the 22% card. Remainder: $0. Wants absorbed the squeeze; savings stayed above the 5% floor.
Deliverable
Produce a filled zero-based budget using the template: every line has a dollar amount, sinking funds appear as monthly line items, bucket percentages are computed against take-home, the remainder equals zero, and a one-line note states which adaptation rule (if any) was applied and why.
Do NOT
- Do not budget from gross income; only take-home pays bills.
- Do not accept remembered spending figures when statements are available - memory undershoots.
- Do not leave irregular annual costs out because they are not "monthly"; they are why budgets break.
- Do not balance by cutting needs while wants are untouched, or by silently zeroing savings.
- Do not treat a consistently blown category as a discipline failure; resize it and rebalance.
- Do not decide debt-vs-savings priority here - that ordering belongs to financial-planner.
Quality bar
- The budget sums to exactly zero against take-home income.
- Every irregular expense the user named appears as a sinking-fund line.
- Bucket percentages are shown, and any deviation from 50/30/20 cites an adaptation rule.
- Variable-income users have the 3-month-average baseline documented.
- The review cadence and the 15%-for-two-months resize rule are stated in the handoff.
Escalation
This is general financial education, not individualized financial advice. For self-employment income, major life transitions, or debt loads where minimums crowd out essentials, recommend a certified financial planner or nonprofit credit counselor.