RosterChief/BILLING.md

Platform billing — design

How RosterChief charges a club, and what happens when a club doesn't pay.

This is the design for a revision of the billing subsystem, not a rewrite. ARCHITECTURE.md covers the club-owned domain; billing is the other direction — the platform charging the tenant — and has never been documented there. Once this design is implemented, §4 (the model) gets folded into ARCHITECTURE.md and this file keeps the lifecycle and operational detail, the same split DEPLOYMENT.md already has with the rest of the docs.

Status: proposed, not implemented. Nothing in §4–§9 exists on disk yet.

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1. What ships today, and what's actually wrong with it

The existing implementation (billing/) is structurally sound. Three things in particular are worth keeping and are not up for renegotiation in this redesign:

• Snapshot-on-Due. Due.tier and Due.amount are frozen when the period opens and never read back through the plan at display time. Raise a price and last year's invoice still says what was actually charged. This is the single most important property in the subsystem — a live lookup would rewrite financial history.
• Dated prices. TierPrice.active_from means a rate change is one new row with a future date, not an edit to an existing one. Every period already opened keeps its amount.
• Asymmetric commands. archive_overdue_clubs reports by default and only acts with --commit; renew_subscriptions acts by default and only previews with --dry-run. The asymmetry is deliberate and correct: not archiving is a safe failure, not renewing is a silent revenue leak.

What's wrong is narrower than "the approach": three hardcoded assumptions, all in billing/models.py.

#	Today	Problem
1	Due.save() → add_one_year(period_start)	Every plan is annual. Duration is only overridable by passing an explicit period_end, which is the hack trials use.
2	GRACE_DAYS = 45, module constant	One grace period for every plan, editable only by deploying code.
3	grace_until = period_end + GRACE_DAYS	The clock runs from the wrong end. A club uses the entire unpaid year and then gets 45 days — roughly 410 days of unpaid use before archive_overdue_clubs will touch it.

Item 3 is the real defect. The requested behaviour — "unpaid → warned → archived after N days" — isn't a tweak to the current rule, it's the opposite of it.

A fourth gap is in the UI rather than the model: the club-facing banner (management/views.py:89-93) fires on the period ending, not on money being owed. A club that owes money is told nothing.

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2. Target lifecycle

                    ┌──────────────────────────────────────────┐
                    │                                          │
   [no plan] ──► TRIAL ──────► UNPAID ──► IN GRACE ──► OVERDUE ─┴─► ARCHIVED
                  │              │  ▲         │           │            │
                  │              │  │         │           │            │
                  └──────────────┘  │      payment     payment    reactivate
                   auto-converts    │         │           │       (+ new period)
                   on renewal       │         ▼           ▼            │
                                    │       PAID        PAID           │
                                    └──────────────────────────────────┘
                                              renewal opens
                                              the next period

Trial. A club starts on a trial plan (there can be several — a 1-month and a 3-month trial are just two plans). It carries a price of 0, so it settles itself the moment it opens and can never make a club archivable. When the trial period runs out, the next renewal converts the subscription onto the pre-selected paid plan. This already works (open_period's trial-conversion check) and is kept as-is.

Unpaid. Every paid period — new or renewed — opens UNPAID with an invoice attached. From that moment the club's admins see a warning on their management home page. This is the state the whole redesign is about.

In grace. The period has started and is still unpaid. The warning escalates and gains a countdown: "Your club will be archived in N days."

Overdue. Past grace_until. archive_overdue_clubs will now pick this club up — subject to Subscription.auto_archive, which stays as the manual override for a club you're negotiating with.

Archived. Club.archive() sets archived_at. The subdomain stops resolving (ClubTenantMiddleware.get_club() filters on Club.objects.active()), so the club is frozen exactly as requested: no access, nothing destroyed. Reactivation is a deliberate platform-admin action.

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3. The three clocks

Every plan carries three numbers. Getting them confused is the easiest way to misread this design, so they are named for what they measure from:

Field	Measured from	Answers
duration_months	period_start	How long is a period?
renewal_lead_days	period_start, backwards	How early is the invoice raised?
grace_days	period_start, forwards	How long may it stay unpaid?

grace_days runs from the period start, not from the invoice and not from the period end. That is the decision this redesign turns on. It means the warning window is renewal_lead_days + grace_days — the club is told before the period begins and gets a further grace once it has, but is cut off partway into a period it never paid for.

Worked timelines

ANNUAL      duration 12mo · lead 30d · grace 30d
            period 1 Jan 2027 – 31 Dec 2027

  2 Dec 26      1 Jan 27      31 Jan 27              31 Dec 27
     │             │              │                       │
  INVOICE     PERIOD STARTS   grace ends              PERIOD ENDS
     │─────────────│──────────────│
      30d warned    30d grace     └─► ARCHIVED 1 Feb 27 if unpaid
     └──────────── 60 days of warning ────────────┘


QUARTERLY   duration 3mo · lead 14d · grace 30d
            period 1 Jan 2027 – 31 Mar 2027

  18 Dec 26     1 Jan 27      31 Jan 27      31 Mar 27
     │             │              │              │
  INVOICE     PERIOD STARTS   grace ends    PERIOD ENDS
     └──────── 44 days of warning ───┘


MONTHLY     duration 1mo · lead 7d · grace 14d
            period 1 Jan 2027 – 31 Jan 2027

  25 Dec 26   1 Jan 27   15 Jan 27   31 Jan 27
     │           │           │           │
  INVOICE   PERIOD ST.  grace ends  PERIOD ENDS
     └─── 21 days of warning ─┘

Why the lead time has to be per-plan

Today's single RENEWAL_LEAD_DAYS = 30 is silently annual-only. On a 1-month plan it would issue the next period before the current one had started — periods would run away from the calendar within a couple of cycles. Any plan shorter than 30 days is broken by a global constant, which is why renewal_lead_days moves onto the plan.

Guardrails

Two invariants, enforced as CheckConstraints. duration_months × 28 is the conservative lower bound on days in that many months, which keeps the check expressible in SQL:

• renewal_lead_days < duration_months * 28 — or the next invoice precedes the current period.
• grace_days <= duration_months * 28 — or a club can never be archived before its next period is issued, and unpaid periods silently stack.

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4. Model changes

4.1 Tier → Plan (rename)

The code says Tier, every spec and screen says "plan". Renaming now, while only ~80 references exist, is cheaper than carrying the mismatch. TierPrice → PlanPrice follows, as do the FK field names (Subscription.tier → plan, Subscription.post_trial_tier → post_trial_plan, Due.tier → plan, PlanPrice.tier → plan).

4.2 Plan — new fields

class Plan(UUIDModel):
    name, slug, description, is_active          # unchanged

    duration_months    = PositiveSmallIntegerField(default=12,  validators=[MinValueValidator(1)])
    renewal_lead_days  = PositiveSmallIntegerField(default=30)
    grace_days         = PositiveSmallIntegerField(default=30)
    is_trial           = BooleanField(default=False)

is_trial is an explicit flag rather than "price == 0" — a genuinely free tier is not a trial, and the two dropdowns on the trial form need to offer different sets of plans. It also lets the control panel keep trial plans out of the normal "change plan" picker.

price_on(day) is unchanged.

4.3 Due — derivation changes, fields don't

def save(self, *args, **kwargs):
    if not self.period_end:
        self.period_end = add_months(self.period_start, self.plan.duration_months) - timedelta(days=1)
    if not self.grace_until:
        self.grace_until = self.period_start + timedelta(days=self.plan.grace_days)
    super().save(*args, **kwargs)

grace_until stays a stored field. That is what makes it a snapshot: editing a plan's grace_days afterwards must not move the archive date of a period that is already running, for the same reason amount is frozen. Storing the computed date rather than the input days gets this for free — no extra column needed.

The predicates change meaning even though only one changes shape:

def is_in_grace(self, today=None):      # period running, unpaid, not yet archivable
    return self.is_owing and self.period_start <= today <= self.grace_until

def is_overdue(self, today=None):       # unchanged logic, new meaning of grace_until
    return self.is_owing and self.grace_until < today

def days_until_archive(self, today=None):   # new — drives the countdown in the banner
    return (self.grace_until - today).days

is_in_grace previously required period_end < today; it now requires period_start <= today. An owing due before its period starts is neither in grace nor overdue — it is simply issued, which is the gentlest of the three warning levels in §6.

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5. Price changes

Already correct, and worth stating precisely because the interaction with lead time is not obvious.

open_period snapshots plan.price_on(period_start) — the price in force on the day the period starts, not the day the invoice is raised. Add a PlanPrice with active_from = 1 Jan 2027 and every period starting on or after that date bills at the new amount. That is exactly "adjust the price, effective as of the club's next billing cycle".

The edge case that will bite: periods are issued renewal_lead_days early. Enter a price change on 15 December for periods starting 1 January, and any annual period already issued on 2 December keeps the old amount — its Due.amount was frozen two weeks before the new price existed. The snapshot is behaving correctly; the operational rule is what matters:

Enter a price change before the renewal lead window opens for the periods it should apply to.

Two mitigations, both recommended:

1. Document the rule where prices are added (control-panel help text).
2. Warn in the control panel when a new PlanPrice.active_from falls inside a period that has already been issued, naming the affected clubs. Correcting one is then a deliberate cancel-and-reopen, not a silent surprise.

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6. The club-facing warning

A new service — billing/services/notices.py — returns one small object for a club, or None:

@dataclass(frozen=True)
class BillingNotice:
    level: str                  # "info" | "warning" | "error"
    due: Due
    amount_outstanding: Decimal
    grace_until: date
    days_until_archive: int

Condition	Level	Message
Owing, today < period_start	info	Invoice outstanding, due by grace_until.
Owing, in grace, > 7 days left	warning	Fees are due. Club will be archived in N days.
Owing, in grace, ≤ 7 days left	error	Final notice. Archived in N days.
Owing, overdue	error	Archiving is pending.
Nothing owing	—	No banner.

Rendered in management/home.html, in the existing alert block, and gated on is_club_admin the same way the current billing banner is — ordinary members have no business seeing platform billing. The existing "your period ends soon / renews automatically" notice is kept, at lower priority: it answers a different question and only shows when nothing is owed.

All strings go through {% trans %} / {% blocktrans %} with %(name)s-style placeholders per CLAUDE.md — the countdown is a {% blocktrans count %} so the plural form survives translation.

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7. Services and commands

billing/services/dues.py:

Function	Change
subscribe(club, plan, …)	Rename only.
start_trial(club, trial_plan, *, post_trial_plan, start=None, …)	Drop trial_months — the trial's length is now trial_plan.duration_months, and period_end no longer needs to be passed explicitly.
open_period(…)	Duration and grace come from the plan. Trial-conversion check unchanged.
next_period_start	Unchanged.
dues_in_grace(today)	owing_dues().filter(period_start__lte=today, grace_until__gte=today).
dues_overdue(today)	Unchanged.
archivable_clubs(today)	Unchanged.
subscriptions_due_for_renewal(today, lead_days=None)	Per-plan lead. See below.

subscriptions_due_for_renewal currently compares every subscription against one horizon in SQL. With a per-plan lead the comparison is per-row. The function already materialises its result as a Python list comprehension, so the honest move is to keep doing that and compare against each plan's own lead:

latest_period_end is None or latest_period_end <= today + timedelta(days=subscription.plan.renewal_lead_days)

At platform scale (tens to low hundreds of clubs) this is one query plus a list walk; pushing portable date arithmetic into SQL to save that is not worth the opacity. The command's --lead-days flag stays, redefined as a global override of the per-plan value, which is what makes backfills and rehearsals possible.

archive_overdue_clubs needs no changes — but note that with the clock moving from ~410 days to ~60, this job goes from theoretical to load-bearing. Its dry-run-by-default posture matters more now, not less, and DEPLOYMENT.md's advice to run it without --commit for the first week should be re-followed after this ships.

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8. Migration plan

Four steps, in order. Step 3 is the one that can take down live clubs.

1 — Rename. RenameModel + RenameField operations. makemigrations will prompt for each ("Did you rename …?"); answer yes. Inspect the generated migration by hand before running it — if Django emits DeleteModel + CreateModel instead of RenameModel, it will drop every price, subscription and due in the table. This is the single highest-risk step in the change.

2 — Add the new Plan fields, with defaults chosen to reproduce today's behaviour on existing rows: duration_months=12, renewal_lead_days=30, is_trial=False. grace_days defaults to 30, not 45 — the number is not being carried over, because the thing it measures from has changed.

3 — Do NOT backfill grace_until on existing dues.

An open annual period that started in, say, March would today have grace_until around the following February. Re-derived under the new rule it becomes March + 30 days — a date already in the past. Every such club becomes instantly overdue, and the next archive_overdue_clubs --commit run switches off the entire paying customer base overnight.

Existing Due.grace_until values are snapshots and must be left exactly as they are. Only periods opened after this ships use the new rule; every club migrates onto the new terms naturally at its next renewal. If a specific club should move sooner, that is a deliberate one-off (cancel the open period and reopen it), not a bulk data migration.

4 — Retire the constants. GRACE_DAYS and RENEWAL_LEAD_DAYS become the default= values on the new Plan fields and are deleted from billing/models.py.

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9. Blast radius

Everything below references Tier, the constants, or the grace semantics, and will need touching:

Area	Files
Models & services	billing/models.py, billing/services/dues.py, new billing/services/notices.py
Commands	billing/management/commands/renew_subscriptions.py
Admin	billing/admin.py
Control panel	controlpanel/views.py (20 refs), forms.py (10), urls.py (3), services/statistics.py
Control-panel templates	billing.html, _club_billing_card.html, _club_health_table.html, dashboard.html
Club-facing	management/views.py, management/templates/management/home.html
Invoice	billing/templates/billing/invoice.html
Tests	billing/tests.py (16), controlpanel/tests.py (17), management/tests.py (3), formbuilder/tests.py (1)
Docs	ARCHITECTURE.md (new billing section), DEPLOYMENT.md (archive job note)

controlpanel/services/statistics.py deserves particular attention: tier_name, dues_grace_until and dues_period_end all feed the club-health table, and dues_in_grace() / dues_overdue() feed the dashboard counters. Their numbers will move once the clock changes, which is expected — but the annotations themselves need renaming, not just re-pointing.

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10. Decisions taken, and the ones still open

Taken:

• Grace runs from period_start. (Alternatives considered: from invoice issue — strictest, archives a club before it has used anything; from period_end — today's behaviour, ~410 days of unpaid use.)
• Lead time is a per-plan field. (Alternatives: derived from duration — invisible in the admin; one small global constant — too tight for an annual invoice paid by bank transfer.)
• Tier → Plan.
• Trial length comes from the trial plan's own duration_months, not a per-subscription number.
• post_trial_plan stays on Subscription, not on Plan — the same trial can convert to different paid plans for different clubs.

Still open — worth deciding before implementation:

1. Does full payment auto-restore an archived club? Today reactivate() is explicit. Automatic restoration is friendlier ("they paid, let them back in") but requires knowing the club was archived for non-payment rather than by hand — which means an archived_reason field. The cheap version is to leave it explicit and surface a prominent "Reactivate" action on any archived club whose dues are now settled. Recommend the cheap version.
2. Banner placement. management/home.html only, or persistent in management/base.html? Home matches the request; base is harder to ignore in the final week.
3. Email reminders. Out of scope here — the request is for an in-app warning — but a send_billing_reminders command is the obvious follow-up, and the BillingNotice service in §6 is deliberately shaped so it could feed one without rework.
4. Online payment. Entirely out of scope. Every payment is still recorded by hand by a platform admin (record_payment). Worth knowing that the warning tells a club admin money is due while giving them no way to pay it in-app.