The practices
| Practice | Evidence (source, year, finding) | Verdict for our form | How on our form |
|---|---|---|---|
| Review screen before the final submit | GOV.UK, question pages, read 2026: a check-your-answers step cuts errors and raises confidence before sending | Apply now: this is a legal filing, a slip should be caught before it is sent | Add a summary of all twenty answers with change links, between Submit and the confirmation screen |
| Error summary at the top, focus moved to it | GOV.UK, validation pattern, read 2026: list every error, move focus to the list, mark the page title "Error:" | Apply now: the twin has per-field messages but nothing catches focus at submit | On submit, list the failed fields above the first card and move focus there |
| Save the filing and come back later | GOV.UK One Login, 2025: a save-and-complete-later link sits under the primary action | Apply now: an operator waiting on a launch reference should not lose twenty filled fields | Add "save and finish later" next to Submit; keep the draft in the browser's own storage |
| Never ask twice for what the filer already gave | WCAG 2.2, success criterion 3.3.7, published 5 October 2023: auto-fill or offer a prior answer, do not re-ask | Apply later: waits on operator accounts across filings, not part of the twin yet | Once accounts exist, the launching-State and operator block fills from the filer's last object, not just today's default |
| Mark a helper-filled value until confirmed | Shape of AI, auto-fill pattern, 2026: keep a visible mark on a machine-suggested value until accepted or overridden | Apply now: the helper names its source, but a filled field looks the same as one the filer typed | Give a field the helper just wrote a light mark that clears on the filer's first edit or accept |
| Fill what can be guessed, ask the rest | Adam Silver, Form Design Patterns, 2018 to 2024: sensible defaults cut the questions a filer must answer | Apply now, already matches | Today's date and Cyprus as launching State are pre-set; extend to any field with an obvious default |
| A long option list gets a typed search, never a dropdown | Baymard, drop-down usability and country selector, read 2026: scrolling 200 options fails on mobile and breaks tab order | Apply now, already matches | Country, launch site and vehicle already use a typed list; keep this the rule for any new list field |
| Validate on leaving the field, plain words, never mid-typing | NN/g, ten guidelines for form errors, 2019, reviewed December 2024 | Apply now, already matches | Pattern, unit and web-address checks already fire on blur with a plain sentence |
| Reveal a follow-up field only when it applies | GOV.UK, conditionally revealed questions, 2021 to 2026 | Apply now, already matches | The "cannot be reached" checkbox already swaps a reference field for an upload field |
| Tell the browser and the password manager what a field means | WCAG 2.2, success criterion 1.3.5 and GOV.UK date input, 2023 to 2026: an autocomplete token lets stored data fill the field | Apply now | Give operator name, email and address their autocomplete token; keep autocomplete off only on the three typed-list fields |
| Group related controls under one legend | USWDS, form guidance, read 2026: a fieldset and legend let a screen reader announce the group once | Apply now | Wrap each proof block and its offline checkbox in a fieldset named after the proof |
| Every clickable control is at least 24 by 24 pixels | WCAG 2.2, success criterion 2.5.8, published 5 October 2023 | Apply now, check: the help icon is specified at about 18 pixels | Measure the help icon and offline checkbox on screen; pad to 24 pixels if the drawn icon stays small |
| One question per screen | GOV.UK, question pages, read 2026: proven at scale for a one-off, unfamiliar task | Not for us: see disagreements below | Kept as the sectioned single page it already is |
| Validate only at final submit, never on leaving a field | GOV.UK, validation pattern, read 2026 | Not for us: see disagreements below | Kept as on-blur validation, plus the new error summary above |
| A remembered date gets three typed boxes, not a calendar | GOV.UK, date input, read 2026 | Not for us: see disagreements below | Launch date stays a calendar field |
| Chat-style, one-question-at-a-time filling | Formester, 2026 form trends: lifts completion 15 to 25 percent on short lead forms | Not for us: twenty technical numbers do not fit a spoken back and forth | The filing helper stays a panel the filer reads and corrects, not a conversation |
| No memory test to sign in | WCAG 2.2, success criterion 3.3.8, published 5 October 2023 | Not for us: this form carries no sign-in step today | Revisit once operator accounts exist, alongside save and resume |
What the sources disagree on
One question per page, or a sectioned single page
GOV.UK and Adam Silver both push one thing per page, proven at large scale for a public, unfamiliar task. But GOV.UK's own guidance allows grouping "when user research tells you," and names our exact case: a service for users who repeat the task and move between fields fast. Our filer is a professional, filing the same twenty fields once or twice a year with a folder of documents open. Keep the sectioned single page. Add the check-your-answers screen so the review benefit of one-thing-per-page arrives without the extra clicks.
Validate on leaving a field, or only at the final submit
Carbon, Polaris, Material and NN/g validate as the filer leaves a field. GOV.UK's own pattern says the opposite: wait for the continue or submit click, because a field left half-typed should not be judged early. Keep validating on blur: our fields carry shapes and ranges (a designator's pattern, an orbit's numbers) that are easy to mistype and hard to find later across twenty fields, and catching the shape while the source document is still open beats catching it once, at the end, all at once. Add the error summary at submit as the safety net GOV.UK is really arguing for.
A calendar picker, or three typed boxes, for a date
GOV.UK recommends three boxes for a date the person already knows, such as a birth date. Kennedy's rule gives a near-future date a calendar and a wide-spread date a text field. Launch date is neither purely remembered nor purely browsed: the filer checks it against the launch provider's record. Keep the native calendar, since the filer is confirming a date, not reciting one from memory.
What is new in 2025 and 2026
- Prefill from an uploaded document is now expected, not a novelty. The newest guidance is about trust, not capability: keep a visible mark on a machine-filled value until the filer confirms it. Shape of AI, auto-fill pattern, 2026.
- Save and resume is moving from a browser cookie to a real identity. GOV.UK's own sign-in now carries a save-and-complete-later link, so a returning filer is recognized, not just remembered by the browser. GOV.UK One Login, 2025.
- USWDS pulled its own Validation component after finding it caused more usability and accessibility problems than it solved; guidance now favors contextual help text over a dedicated validation widget. USWDS, validation, read 2026.
- The three form-specific WCAG 2.2 rules, no repeated entry, no memory test to sign in, a 24-pixel minimum target, moved from new to expected in audits between their 2023 publication and 2026. W3C, WCAG 2.2, published 5 October 2023.
- Chat-style, one-question forms now show a measured lift for short lead forms; not yet for technical filings. Formester, 2026 form trends.
The twin's form against this list
Already does
- Numbered section cards with a rail that ticks a section once its required fields are filled
- One legend for the required-field asterisk, never repeated
- A typed, searchable list for country, launch site and vehicle, no dropdown
- Sensible defaults filled in already: today's date, Cyprus as launching State
- Validation on leaving the field, in plain words, never a code
- A named filing helper that states its source per value and lets the filer accept or correct it
- A conditional reveal at work: the offline checkbox swaps the reference field for an upload field
- A calendar date field read back day first, next to the picker
- A confirmation screen naming the next step and giving a reference
Lacks
- No check-your-answers review screen before the final submit
- No error summary at the top of the form, no focus move on submit
- No save-and-resume; a closed tab loses twenty filled fields
- No mark on a value the helper just filled; once it sits in the field it looks hand-typed
- No autocomplete token on the ordinary text fields, so a browser cannot offer to fill them
- No confirmed 24-pixel target size on the help icon and the offline checkboxes
- No stored operator profile, so the launching-State and operator block is retyped on every new filing
Read next: what the private sector does, and the rules this evidence feeds into, in how a form is built here.