Drop in a formula. Watch it solve.
Tag a number field, write =qty * price * (1 + hst), watch it recalculate live as the signer enters values. SUM, IF, ROUND, AND/OR, MAX/MIN, plus Canadian-tax helpers HST/GST/PST baked in. The signer can't fudge the math — the formula is the receipt.
Live math at the moment of signing.
Calculated fields turn your PDF into a working spreadsheet. The signer fills in inputs, Ink. computes the totals — instantly, transparently, on the signed document.
Excel-style formulas.
All the operators and functions you already know. =qty * price + IF, SUM, ROUND, AND/OR.
Live recalculation.
Totals update as the signer types. No save, no submit, no refresh — just instant math.
Canadian tax built-in.
HST(), GST(), PST() helpers. One template handles every province's tax variant.
Write the formula once, the signer sees the answer.
Compose formulas with tag autocomplete.
Pick fields by name — Ink. inserts the tag. Type=to start a formula, mix tags with operators and helper functions. Live preview shows the value before you save.
Totals fill themselves, the signer just confirms.
Editable inputs are obvious. Calculated cells animate when they update. Tap the tooltip on any total to see the exact formula and inputs behind the number.
Formulas signers can't fudge
Calculated fields are read-only at signing time. The formula runs, the number lands, the signed PDF carries the result. The signer agreed to the math, not a typo.
Tag-pick autocomplete.
Don't memorize cell references. Pick fields by name from a dropdown. The formula composes itself.
Conditional totals.
=IF(province="QC", subtotal * 1.14975, subtotal * 1.13). One template, every province.
Bake the calc into the PDF.
The final computed value is flattened into the signed document and recorded on the cert page with the formula.
See the math, not just the total
Every input row's contribution shown. Subtotal, tax, total — broken out. No mystery numbers, no calculator on the side, no awkward 'wait, let me check that' moments.
Tax automatically applied.
HST in ON/NB/NS/NL/PEI, GST + PST in BC/SK/MB, GST only in AB/NWT/NU/YT. The formula picks the right one from a province dropdown.
Sign with confidence.
Live recalculation means the signer sees what they're agreeing to update in real time as they fill inputs.
Audit-cert-ready.
The formula and the inputs used are recorded on the audit certificate, alongside the final value. Defensible math.
Where Calculations earn their keep.
Anywhere the price isn't fixed — quantities, hours, tax variants, conditional add-ons. The formula stays one source of truth, the signer sees the verified total.
Sales orders
Quantity × unit price + HST. One template, every customer.
Retainer agreements
Deposit auto-calculates as a percent of the agreed total.
Real estate offers
Purchase price → Ontario land transfer tax via tiered IF().
Consulting SOWs
Hours × hourly rate + per diems + applicable provincial tax.
Construction estimates
Materials + labor + waste % + tax — all live.
Medical billing intake
Procedure × code rate, patient share calculated by coverage %.
Investor share subscriptions
Investment ÷ share price = shares issued. Type the cheque amount, the cap-table math auto-fills — rounded down to whole shares, fractional residual logged.
Questions, answered.
What formulas do you support?
All standard Excel operators (+, -, *, /, ^, %), comparison (=, <, >, <=, >=), logical (IF, AND, OR, NOT), aggregates (SUM, AVG, MAX, MIN, COUNT), math (ROUND, ABS, FLOOR, CEIL), text (CONCAT, LEN, UPPER, LOWER), plus Canadian-tax helpers HST(), GST(), PST(), and ISBLANK() for graceful empties.
Can the signer edit calculated fields?
No. Calculated fields are read-only at signing time — only the input fields are editable. The formula auto-updates the calculated value as inputs change. This is what makes the math defensible.
What if a referenced field is blank?
The calculation shows an em-dash (—) until all required inputs are filled, then recalculates. Optional inputs can be wrapped in ISBLANK() or IF(ISBLANK(x), 0, x) for sensible defaults.
Does this work across pages?
Yes. Tag a field on page 1, reference it from page 7 — Ink. resolves references by tag, not by location. Tags are unique per signer.
Is the calculation captured on the audit certificate?
Yes. The final computed value is baked into the signed PDF and the audit cert records the exact formula, the input values used, and the timestamp the math was sealed. Defensible if challenged.
Can calculations drive the Stripe Payment field?
Yes (Firm tier). The Pay field can read its amount from any calculated field, so the charge always matches the agreed total. No mismatch between what the signer agreed to and what gets debited.
How does this compare to other e-signature platforms?
Most platforms either ship basic calculations behind their highest tier or require a paid enterprise SKU for formula fields — and none include Canadian-tax helpers (HST / GST / PST) out of the box. Ink. ships Excel-grade math + Canadian tax + audit-cert traceability in Solo. Drop in a formula, the math is the receipt.
Still have questions?
Email us →Math you can sign on the dotted line for.
Drop a formula. Watch it solve. Sign the math, not the typo. Excel-grade calculations with HST / GST / PST built in — try it free, no card, no trial timer.