Payment-change checker
Each annual change is divided by 12. The shortage is divided by the selected repayment months. Those components are added and compared with the actual old-to-new monthly payment change. A difference within $2 is treated as normal statement rounding; larger differences are marked for review.
Monthly mortgage and escrow check
The monthly check adds principal, interest, escrow, mortgage insurance, and fees, then compares that allocation with the payment credited. It also checks that beginning principal minus principal applied equals ending principal. Exact accounting comparisons allow two cents for currency rounding.
When entered, a simple interest estimate equals beginning principal multiplied by the annual rate and divided by 12. Differences greater than $2 are shown for confirmation because payment timing, adjustable rates, modifications, and loan terms may legitimately produce another amount. Expected escrow deposits and disbursements also use a $2 comparison tolerance.
A fee or suspense balance is shown for review but is not labeled improper. A saved monthly summary is optional, remains in local browser storage, and is not used by the calculation engine.
Monitoring planner
The planner turns dates entered by the homeowner into a local checklist for mortgage statements, property-tax bills, insurance renewals, annual escrow analyses, mortgage-insurance reviews, and servicing transfers. Due-soon and overdue labels are date comparisons only. Nothing runs in the background and MortgageWhy does not connect to a bank, servicer, insurer, or tax authority.
12-month escrow analysis checker
The checker uses the entered computation-year starting month and expands each recurring item into the applicable payment months. Its base monthly collection annualizes only the ordinary recurring payments scheduled in that computation year, so an item that begins or ends midyear is not collected for inactive months. Supported two- and three-year items are spread across their applicable funding cycle. It creates 12 month-end balances, applies the deposit before bills entered for that month, and compares the lowest balance with the selected cushion.
A shortage is reported when a nonnegative current balance is below its target. A deficiency is reported only when the entered current balance is actually negative. The repayment view separately enforces the federal shortage and deficiency option matrix or labels a different schedule as a voluntary what-if. Surplus language depends on payment status and the $50 threshold.
This follows the structure of aggregate escrow analysis but cannot reproduce information that was not entered, including precise transaction dates, state limits, servicer timing conventions, loan-document provisions, or corrections.
Annual statement review and action report
The statement review recomputes the entered balance roll-forward, checks the computation-year dates and selected federal decision rules, and identifies missing facts. Its four outcome labels describe the information entered; they are not legal conclusions. Uploaded PDFs and images are read in the browser and every extracted figure must be confirmed before use.
Mortgage-servicing rules checker
The rules checker selects a structured federal rule entry by topic. Each entry records its citation, official source, source-check date, evidence needed, and key exceptions. If payment status, loan type, property state, or mortgage-document terms could change the answer, the tool identifies that missing information instead of producing a compliance conclusion. State law and loan-program rules are not yet encoded.
Servicer letter generator
The generator prepares an editable information request, notice of error, or combined draft from facts supplied by the homeowner. It requires confirmation of the servicer's designated address, never sends the letter, and leaves the user responsible for accuracy, attachments, delivery records, and deadlines.
Property-tax assessment review
Five deterministic screens compare user-confirmed inputs: assessor market value against valuation evidence; pre-exemption assessed value against a confirmed local assessment ratio; subject assessed value per square foot against the median of at least two entered same-cycle comparable assessments; and eligible exemptions or property-record mismatches; and assessor market value against the range mechanically indicated by user-entered comparable sales. Each screen returns a possible ground, no indicated ground, or missing-information result with a separate confidence label.
The optional tax-change decomposition separates the entered annual bill change into taxable-value, effective-rate, special-assessment, and unreconciled components. When explicit effective rates are omitted, they are derived from the entered annual bill less entered special assessments, divided by taxable value. The assessment-cap screen applies only when the homeowner confirms a cap, prior limited value, annual percentage, proposed market value, and rate. It does not encode portability, reset events, classifications, or local exceptions.
The default 5% value-gap and 10% comparable-premium settings are visible screening thresholds, not legal standards. The expected assessment ratio and filing deadline must be confirmed from official local guidance. The optional tax-impact estimate applies the current effective tax rate to an entered proposed taxable value and therefore may differ from a real corrected bill that includes caps, exemptions, special assessments, fixed charges, or rate changes. The generated letter is supporting material and does not replace a locally required petition, portal submission, fee, or hearing request.
The assessment-review offer in the escrow result appears only when the property- tax increase is at least $25 per month and is not smaller than another positive recurring escrow-cost driver. Shortage repayment is excluded from this dominance test because it is a temporary financing component rather than an underlying bill.
Payment-change routing and private share card
After the existing escrow calculation runs, a deterministic router gives an unexplained difference priority over cost-reduction paths. Otherwise it compares only positive entered tax, insurance, shortage, and other-escrow changes. A clear largest driver determines the first next step; changes within the calculation's rounding tolerance use a combined-driver result. The property-tax path continues to require the material tax-driver offer threshold described above. The router does not change the calculation or decide that a bill or servicer action is wrong.
The optional share card is generated in the browser from fixed categorical result language. Its default model contains no entered amount, address, account information, property fact, document detail, or calculation date. MortgageWhy does not upload or publish the card automatically.
The planned $29 property-tax packet is an interest test, not a product for sale. It appears only after a possible ground supported above low confidence and is suppressed for modeled no-immediate-cap-savings results, rate-or-fixed-charge- only increases, and entered purchase or new-construction reset events. The control visibly states that nothing is available for purchase and collects no email or payment information.
Biweekly payment comparison
The comparison models contractual biweekly crediting, a withdrawal plan that holds half-payments until a full monthly payment is available, semimonthly payments, and a monthly payment plus one-twelfth extra principal. Each scenario amortizes the entered principal at the entered rate using its stated crediting frequency, adds plan fees, and compares payoff time, interest, and net savings. It is a planning comparison; the loan agreement and servicer's actual crediting practice control.
Pre-closing escrow guide
The guide organizes entered loan type, escrow requirement, estimated taxes and insurance, initial deposits, prepaids, cushion, waiver pricing, and reserves. It highlights questions to ask but does not decide whether escrow is legally required or whether a waiver is economically best.
Shortage, tax, insurance, and surplus tools
- August 13, 2026: Added monthly whole-mortgage consistency checks.
- August 13, 2026: Added the plain-English mortgage escrow rules guide.
- Shortage repayment = remaining shortage ÷ repayment months.
- Monthly tax change = annual tax change ÷ 12.
- Monthly insurance savings = annual premium savings ÷ 12.
- Known surplus exposure = tax increase + insurance increase.
Refinance comparison
Principal and interest use the standard fixed-rate amortization formula. Simple break-even equals closing costs divided by monthly principal-and-interest savings. The tool does not currently model APR, points, lender credits, escrow, mortgage insurance, tax effects, opportunity cost, or cash-out proceeds.
New-construction tax estimate
Projected annual tax equals expected assessed value multiplied by the entered effective rate, less entered annual exemptions. The possible undercollection is the positive monthly increase multiplied by the number of months entered. It is a planning scenario, not a county assessment forecast.
PMI planner
Scheduled balances use fixed-rate amortization. The planner identifies the first scheduled month at or below 80% and 78% of the original property value. Federal cancellation and termination rules have additional requirements, and FHA, VA, USDA, lender-paid, or nonconforming insurance can follow different rules.
Testing and corrections
Financial calculation functions are isolated from the interface and covered by repeatable unit tests, including increases, decreases, alternate repayment periods, invalid inputs, amortization, and monthly running-balance scenarios. Results should still be checked against official documents before acting.
Change history
- August 14, 2026: Added deterministic payment-change routing, a client-only privacy-safe share card, property-tax false-positive gates, and a transparent packet interest test.
- August 14, 2026: Added tax-change decomposition, expanded property facts, comparable sales, assessment-cap screening, and a material tax-driver offer threshold.
- August 14, 2026: Added the private property-tax assessment review and printable appeal-kit support.
- August 13, 2026: Added statement review, consumer action reports, and local letter drafting.
- August 13, 2026: Added monitoring, pre-closing, biweekly, and federal rules tools.
- August 13, 2026: Corrected escrow terminology, dates, recurring items, and the federal option matrix.
- August 12, 2026: Added the initial 12-month escrow projection methodology.
- August 12, 2026: Added new-construction and PMI planning methodology.
- August 11, 2026: Added shortage, surplus, tax, insurance, and refinance tools.