Under TaRMS, a taxpayer no longer has a VAT account, a PAYE account and an income tax account — it has one account. The local SSP guide states the concept in two confirmed sentences that this lesson spends its full length unpacking: "Every taxpayer has a Single Account at ZIMRA — a unified ledger across all revenue heads, in both USD and ZiG, that records every assessment and every payment. Payments are not posted directly to a specific tax assessment; they go to the Single Account and are then allocated to specific liabilities by ZIMRA's allocation rules (typically oldest debt first within tax type, then by tax type priority)." The immediate corollary, also confirmed: "it is possible for a payment intended for VAT to be allocated to a prior unpaid PAYE shortfall, leaving the VAT balance unsettled." You do not direct your payments; the ledger does.

The second structural rule is currency segregation: "USD payments and ZiG payments do not net against each other. A USD-stream tax cannot be paid out of a ZiG balance — pay in the currency of the underlying liability." The Single Account is therefore really one account with two parallel ledgers — a USD ledger and a ZiG ledger — that never touch. The legal root is Section 37AA of the Income Tax Act [Chapter 23:06] (separate returns where any part of income is earned in foreign currency, USD as the currency of account) and the VAT Act's Section 38(4) currency-matching rule (pay in the currency of the supply — Delta Beverages 23-HH-577; Inamo 23-SC-096), and the legal ancestor of the allocation rule itself is Section 72(8)'s statutory set-off order, walked in the Taxpayer Account Management lesson.

Operationally, the Single Account is read and worked through two modules. Payments (seven pages): Balance, New Payment (credit card or E-Banking), E-Banking, Payment History, Single Account Transactions (both currencies, by date range), Withdrawal (refunds out of the account) and Withdrawal Application History. Taxpayer Accounting (four pages): Assessment Notices, Audit Assessment Notices, Summary Report (net balance per tax type) and Tax Type Report (every assessment, payment and adjustment). The guide's confirmed discipline: reconcile the Summary Report monthly, because discrepancies "almost always indicate either (a) an unallocated payment that needs ZIMRA to allocate, or (b) an assessment the taxpayer hasn't received notice of and may want to object to" — the first cured through E-Messaging, the second through Case Management inside the 30-day objection window.

The lesson's central warning is the misallocation cascade: one old, small, forgotten debt — even a disputed or migrated one — sits at the head of the queue and silently consumes every subsequent payment, manufacturing fresh arrears on the heads you thought you were paying, failing the ITF 263 real-time check, and triggering the Section 80 30% bleed. The cure is the monthly reconciliation routine; the prevention is keeping every head current — because in a single-account world there is no such thing as being "up to date on VAT but behind on PAYE." There is only one balance, per currency, and it is either clean or it is not.

Under the legacy systems, each revenue head lived its own life: separate accounts, separate payments, separate arrears. A taxpayer could be impeccably current on VAT while an old PAYE balance gathered dust — and a payment marked "VAT" went to VAT. TaRMS abolished that world. The Single Account is the unified ledger at the heart of the system: every assessment from every head posts into it; every payment lands in it; and an allocation engine, not the taxpayer's covering letter, decides what the money settles.

This design is deliberate, and it embodies a policy choice as old as Section 72(8) of the Income Tax Act: the fisc collects oldest-first and refuses to let taxpayers cherry-pick which debts to service. What the statute did within provisional payments, the Single Account generalises across the entire relationship. Three consequences follow before any screen is opened:

1. Per-head compliance thinking is obsolete. The question "is my VAT paid?" has no standalone answer — a VAT-intended payment may have been allocated elsewhere. The only meaningful questions are: what is my net balance per head on the Summary Report, and is the whole ledger clean in each currency?
2. History matters more than intention. Because allocation runs oldest-first, the account's past — including migrated legacy balances (the Old-Period Returns lesson) — governs where today's money goes. An unreconciled account spends your money on debts you may not know you have.
3. Currency is destiny. The USD ledger and the ZiG ledger are sealed compartments. A healthy credit in one currency does nothing for a debt in the other; paying in the wrong currency is, functionally, not paying.

Where this sits in the course: the introduction lesson announced the Single Account and the oldest-first rule; the Taxpayer Account Management lesson (debt course) walked the statutory account logic (Sections 71, 72, 48; Section 37AA; VAT Sections 28, 38, 44; FA Section 4B) verbatim. This lesson is the TaRMS-course treatment: the concept, the screens, the allocation doctrine, the currency rule, and the monthly routine — with the statute summarised where already established rather than re-walked. The next lessons in the queue (Changing Bank Details, Searching Transactions, Account Balances & Statements, Making a New Payment, E-Banking, Withdrawals) each zoom into one page of the machinery this lesson maps.

The Single Account is an administrative construct — no section of either Act names it. But each of its behaviours is a statutory rule wearing system clothes.

B.1 Due dates and interest: ITA Section 71

Section 71(1) fixes when tax is due (the three sources walked in the debt course) and authorises payment "in instalments of equal or varying amounts" at the Commissioner's discretion — the statutory basis of instalment plans. Section 71(2) attaches automatic, continuous interest to unpaid tax from the due date (rates per SI 212/2022 for income tax ; for VAT, the Fifth Schedule as substituted by SI 25/2025 — bank policy rate + 5% local currency, 10% foreign currency, confirmed in the source Regulations), subject to the special-circumstances interest-free extension proviso (MR Bank 19-HH-779). The Single Account is where this interest visibly accrues: every day a debt sits at the head of the allocation queue, it grows.

B.2 The allocation rule's legal ancestor: ITA Section 72(8)

As established verbatim in the Taxpayer Account Management lesson, Section 72(8) directs that provisional-payment credits be applied "successively": first against the year's tax, then against any other amount due, with only the residue refundable. That cascade — your money meets your oldest and broadest obligations before you see any of it back — is the statutory DNA of the Single Account's allocation engine. The guide's formulation of the system rule is: "oldest debt first within tax type, then by tax type priority." Note what is confirmed beyond doubt: payments are not posted to the assessment you intend; they are pooled and allocated by rule.

B.3 The currency wall: ITA Section 37AA and VAT Section 38(4)

Section 37AA (FA 8/2022, confirmed verbatim in the debt course) requires separate returns where any part of income is earned in foreign currency, with the USD as the currency of account and proportional assessment — the income tax root of the dual ledger. On the VAT side, Section 38(4) requires tax to be paid in the currency of the underlying supply (Delta Beverages 23-HH-577; Inamo 23-SC-096; Prosperous Days 21-HH-024), and the PAYE mirror is the 13th Schedule's para 3(1b) separate-currency determination (one P2 per currency, from the PAYE lesson). The guide's operational restatement: "USD payments and ZiG payments do not net against each other… pay in the currency of the underlying liability." Currency mismatch is not a rounding nuisance; on the VAT side, paying in the wrong currency has been treated as non-payment of the matched obligation, with the Section 38(4)/(4a) machinery and the double-forex-tax civil penalty (Section 38A) in the background.

B.4 The exits and the gates: Section 48, VAT Section 44, Section 80, FA Section 4B

A credit in the Single Account has four exits (the debt course's "four exits" doctrine): sit as a buffer, be set off (VAT Section 44(6) cross-head set-off; Section 72(8) cascade), be refunded (Section 48; VAT Sections 44–45 — including Section 44(7): no refund while any return is unfiled; the 30-day refund window in the Regulations, SI 175/2007; 60-day interest under Section 48(3)), or be lost to time (the six-year lattice from the Old-Period lesson). And the account's cleanliness is consumed in real time by the ITF 263 automatic check (previous two lessons): the Single Account is the record that check reads. Finally, Finance Act Section 4B (confirmed in the debt course) governs the pipe into the account: an approved intermediary (your bank) must credit the Consolidated Revenue Fund within 24 hours, on pain of intermediary-level interest (15% USD / policy + 5% ZiG) — so a bank's delay is the bank's cost, and the taxpayer is discharged on paying the intermediary.

C.1 Anatomy: one account, two ledgers, three record types

Picture the Single Account as a T-account per currency. Debits (liabilities in): every assessment — self-assessed returns (Section 37A(10)–(11): the return is the assessment), estimated and additional assessments (Sections 45–47; VAT Section 31), penalties and interest as they accrue, migrated legacy balances. Credits (money and relief in): every payment through any channel, withholding credits (the Section 80 30%, PAYE credits), approved refund-position returns, remissions and successful objections. Allocations: the engine's internal postings matching credits to debits — oldest first within head, then by head priority. The visible surfaces of this anatomy:

(All page inventories confirmed from the local guide. )

C.2 The allocation doctrine, worked

The confirmed rule: oldest debt first within tax type, then by tax type priority — and payments are never posted directly to a chosen assessment. Walk the canonical trap:

Setup. Pamberi Hardware believes itself current. Unknown to the new bookkeeper, a USD 3,000 PAYE shortfall from 14 months ago (an audit adjustment never paid) sits in the USD ledger.

Event. The August VAT 7 is filed showing USD 8,000 due; Pamberi pays USD 8,000 by e-banking, intending VAT.

Allocation. The engine sees an older PAYE debit. Applying its rules, USD 3,000 of the payment (plus accrued interest on the PAYE debt) is allocated to PAYE first; only the remainder reaches VAT. The VAT assessment is now part-paid: roughly USD 3,000-plus short.

Cascade. The unpaid VAT balance accrues Fifth Schedule interest (10% — foreign currency, SI 25/2025) from the VAT due date; the part-payment does not avert the Section 39(2)(a)(i) penalty exposure on the unpaid portion; the next ITF 263 check reads "VAT payment outstanding" and fails — and if the certificate lapses, the Section 80 30% withholding starts on gross receipts. One stale USD 3,000 debt has now disturbed three heads of consequence. (This is the debt course's misallocation cascade, here traced through the screens that reveal it: the Summary Report shows VAT in arrears; the Tax Type Report shows the part-allocation; Single Account Transactions shows the USD 8,000 landing and splitting.)

Doctrinal lessons. (1) You cannot out-pay a dirty ledger — paying current liabilities precisely while an older debt exists merely re-routes money backwards. (2) Reconcile before you pay, not after — the Balance page accepts historical dates precisely so you can establish the position before funds move. (3) Disputed old debts are urgent — a debt you believe wrong (a migration error, an estimate you mean to object to) is not neutral while it waits: it is eating your payments. Route it to Case Management (objection, 30-day window) or E-Messaging (allocation queries) now.

C.3 Currency segregation, worked

Rule (confirmed): USD and ZiG never net; pay in the currency of the underlying liability.

Trap one — the phantom credit. Mukai (Pvt) Ltd holds a ZiG credit equivalent to USD 5,000 (an over-remitted ZiG PAYE run) and a USD 4,200 VAT debt. Net exposure feels positive; legally and systemically, the USD VAT debt is wholly unpaid: interest accrues at the 10% foreign-currency rate, the ITF 263 check fails on VAT payment, and the ZiG credit sits idle. The cures are independent: pay the USD VAT in USD; deal with the ZiG credit through its own exits (buffer against next month's ZiG PAYE, or a withdrawal application).

Trap two — the wrong-currency payment. A clerk pays the USD VAT liability from the ZiG e-banking profile at the interbank equivalent. The ZiG ledger gains a credit; the USD VAT debt remains unpaid — with the Section 38(4) matching rule and the Delta/Inamo line behind ZIMRA's position. The payment was real money; it was not payment of that debt.

Discipline. One payment instruction per currency per cycle (the PAYE lesson's one-P2-per-currency rule generalised); the monthly reconciliation reads the Summary Report per currency; and the bank-details cluster (next lesson) maintains accounts in both currencies so refunds can issue in the currency of the overpayment (the ITF 263 guide's bank-details rule, confirmed).

C.4 The monthly reconciliation routine

The guide's confirmed instruction — use the Summary Report monthly; discrepancies are almost always an unallocated payment or an unnoticed assessment — expands into the routine (consolidating the debt course's eight steps into the TaRMS workflow):

1. Fix the date range (the month just closed); pull the Summary Report per currency.
2. Compare each head's net balance to your own books' expectation (returns filed × payments made).
3. For each discrepancy, open the Tax Type Report and find the first divergent line.
4. Unallocated/odd allocation? Trace the payment in Single Account Transactions and Payment History; raise an allocation query via E-Messaging (the guide names "requests to allocate a misallocated payment" as an E-Messaging use case, confirmed).
5. Unrecognised assessment? Pull it from Assessment Notices (or Audit Assessment Notices); if wrong, lodge the objection via Case Management — the 30-day window runs from the assessment notice date (Section 62/Section 51; the guide's confirmed warning: "track the deadline carefully and lodge well before it").
6. Confirm no head shows arrears that would fail the next ITF 263 check; cure anything found (returns lessons' machinery).
7. Minute the reconciliation (Section 37B-grade record).
8. Diarise: instalment application before due date where a shortfall is coming (Debt Management — the guide confirms ZIMRA "is more receptive to instalment plans for tax that is not yet overdue").

Monthly is the right cadence because the account's consumers run monthly or faster: P2 by the 10th, VAT 7 by the 15th, payment runs by your customers (verifying your ITF 263), and interest daily.

D.1 Individual: the consultant's two-currency year

Rudo invoices local clients in ZiG and a regional client in USD. Section 37AA puts her on separate returns; her Single Account runs both ledgers. Her QPDs must be split by currency stream; her December reconciliation catches a ZiG QPD allocated against an old ZiG presumptive-era balance she had forgotten — the Balance page at a historical date shows exactly when it arose. She queries the underlying entry via E-Messaging (it proves to be a migrated duplicate), has it reversed, and her QPD allocation rights itself. Without the routine, her year-end ITF 12C would have shown a phantom QPD shortfall — deficits deemed unpaid (Section 72(10), Redan 23-HH-637).

D.2 SME: the cascade caught in month one

Pamberi (the C.2 example) institutes the routine after its USD 3,000 lesson: reconcile on the 5th, pay P2 on the 8th (before the 10th), VAT on the 12th (before the 15th), each in its currency, each after confirming the Summary Report is clean. The next stale item — a USD 240 withholding-tax interest accrual — is caught at month-end as a USD 240 discrepancy, paid for the price of lunch, and never touches the allocation queue. The contrast with the uncaught version (three heads disturbed, certificate risk, 30% bleed) is the entire business case for a routine that costs an hour a month.

D.3 Large corporate: treasury control over one ledger per entity

Mukonde Holdings runs five entities — five TINs, five Single Accounts, ten currency ledgers. Treasury's controls: per-entity payment calendars keyed to the compliance rhythm; dual control on the Payments module (the payment-authoriser role separated under Roles); a group reconciliation pack on the 5th of each month (Summary Reports per entity per currency); instalment applications lodged pre-due-date for any entity facing a shortfall; and a standing rule that no entity pays anything while an unexplained Summary Report discrepancy stands — because feeding a dirty ledger compounds the error. The Section 4B discipline closes the loop: payment is complete when the approved intermediary is paid; a bank that sits on the transfer beyond 24 hours owes the interest, and treasury's proof-of-payment archive makes the point when it matters.

Stated honestly: no reported case addresses the Single Account or its allocation engine as such — the construct post-dates the litigated era in the sources. The authorities attach to the statutory behaviours the account mechanises:

• Delta Beverages 23-HH-577 and Inamo 23-SC-096 (with Prosperous Days 21-HH-024) — the VAT Section 38(4) currency-matching line: pay in the currency of the supply; the segregation rule's litigated backbone.
• Redan 23-HH-637 and SZ 20-HH-142 — the Section 72 QPD machinery (deficits deemed unpaid; the ≤10% underestimate tolerance/waiver) that the account's provisional-tax postings express.
• MR Bank 19-HH-779 — the Section 71(2) special-circumstances interest-free extension proviso: interest relief is possible but exceptional, and it is sought, not assumed.
• Mayor Logistics 14-CC-007 — Section 71(1) instalments as the lawful payment-plan basis (the Debt Management module's statutory root).
• Packers International 16-SC-028 — nil returns: the Summary Report only reflects expectations the profile generates; silence is never compliance.
• The Section 37A line (CF, DNS, IAB, Nestlé) — the return-is-assessment rule that makes your own filings the largest class of debits in the ledger.

The absence of allocation-rule litigation is itself instructive: allocation disputes are resolved administratively (E-Messaging, Case Management) long before they could ripen into case law — provided the taxpayer notices in time. The routine is the remedy.

1. Believing the covering instruction. "Payment for August VAT" on the bank narration directs nothing. Payments pool and allocate by rule. Plan around the rule; never around the narration.
2. Netting currencies in your head. A ZiG credit does not reduce a USD debt — not for interest, not for the ITF 263 check, not at law (Section 37AA; VAT Section 38(4)). Reconcile and pay per currency, always.
3. Leaving disputed or migrated debts "for later." Anything sitting at the head of the queue spends your money today. Object (Case Management, 30 days) or query (E-Messaging) immediately; the Old-Period reconciliation belongs at first access, not at audit.
4. Reconciling annually. The account's consumers run monthly (P2, VAT 7, customer verification of your certificate) and daily (interest). An annual reconciliation discovers cascades after they have compounded — the monthly hour is the cheapest control in this course.
5. Paying while a discrepancy stands. Money into an unexplained ledger position compounds the error and complicates the unwind. Explain first, pay second — the Balance page's historical-date search exists for exactly this.
6. Treating a credit as a refund. A credit has four exits, and the refund exit is gated: application referencing the return (Refund Management), officer review, Section 44(7)'s freeze while any return is unfiled, de minimis carry-forwards, and the withdrawal step to a verified bank account (fraud-sensitive — next lesson). A credit you have not actively managed is a buffer at best and a loss to the six-year clocks at worst.
7. Forgetting the account is what the ITF 263 reads. Every certificate consequence in the last two lessons — automatic refusal, mid-year revocation, the 30% bleed — is downstream of this ledger. Single Account hygiene is clearance strategy.

Work through the questions one at a time. Choose an answer and it is graded immediately, with an explanation and the provision it comes from. Your progress is saved, so you can stop and resume.

• One taxpayer, one account: a unified ledger across all revenue heads, in USD and ZiG, recording every assessment and every payment (guide, confirmed). Per-head compliance thinking is obsolete — there is only the ledger, per currency, clean or not.
• You do not direct payments. They pool and allocate **oldest-first within head, then by head priority — the Section 72(8) cascade generalised. A stale debt at the head of the queue spends your money before your intentions do.
• Currencies never net (Section 37AA; VAT Section 38(4); Delta/Inamo): pay in the currency of the liability; manage each ledger's credits separately; expect refunds in the currency of the overpayment.
• The screens: Payments (Balance — historical dates supported; New Payment; E-Banking; Payment History; Single Account Transactions; Withdrawal ×2) and Taxpayer Accounting (Assessment Notices ×2; Summary Report — the monthly anchor; Tax Type Report — the drill-down).
• Monthly reconciliation is the control: discrepancies are "almost always" an unallocated payment (→ E-Messaging) or an unnoticed assessment (→ Case Management objection, 30 days from the notice). Explain first, pay second; minute everything.
• The misallocation cascade is the threat model: one forgotten debt → part-paid current head → interest (SI 25/2025: policy + 5% / 10% FX) and penalty exposure → failed ITF 263 check → Section 80 30% bleed. Single Account hygiene is clearance strategy.
• Shortfall coming? Instalment application before the due date (Debt Management) — ZIMRA is more receptive pre-arrears (guide, confirmed; Section 71(1)); interest still runs (Section 71(2)).
• No case law on the account itself (stated honestly); the litigated backbone is the currency-matching line, the Section 72 machinery and the return-is-assessment rule.

The Single Account's statutory skeleton

Life of a payment in the Single Account

flowchart TD
 A[Taxpayer pays - New Payment or E-Banking, correct currency] --> B[FA Section 4B: bank credits CRF within 24 hrs - taxpayer discharged on paying bank]
 B --> C[Credit lands in Single Account - visible in Single Account Transactions]
 C --> D{Older unpaid debt in this currency?}
 D -->|Yes| E[Allocated to OLDEST debt first within head, then head priority]
 E --> F[Intended liability part-paid or unpaid]
 F --> G[Interest + penalty exposure on shortfall; ITF 263 check fails; Section 80 30 percent risk]
 G --> H[Monthly reconciliation catches it: Summary Report discrepancy]
 H --> I{Cause?}
 I -->|Unallocated payment| J[E-Messaging allocation query]
 I -->|Unnoticed assessment| K[Case Management objection - 30 days from notice]
 D -->|No| L[Allocated to intended liability - ledger clean]
 L --> M[Certificate check passes; credits exit by buffer, set-off, or Withdrawal]

Statutes & sections

• Income Tax Act [Chapter 23:06] — Section 71(1)–(2) due dates, instalments, automatic interest and the special-circumstances proviso; Section 72(7)–(11) QPD machinery incl. the Section 72(8) successive set-off cascade (allocation's ancestor) and Section 72(10) deemed-unpaid deficits; Section 37AA separate foreign-currency returns, USD currency of account (FA 8/2022); Section 37A(10)–(11) return-as-assessment; Sections 45–47 estimation/additional/additional assessments; Section 48 reduced assessments and 60-day refund interest (SI 212/2022); Section 51/62 assessment notices and 30-day objection; Section 80 withholding engine; Section 37B records. Finance Act [Chapter 23:04] Section 4B — 24-hour intermediary remittance, intermediary interest.
• VAT Act [Chapter 23:12] — Section 28(1) furnish-calculate-pay (15th, FA(No.2) 7/2024); Section 38(4)–(4a) currency matching; Section 39(2)(a)(i) penalty; Fifth Schedule interest as subst. SI 25/2025 (policy + 5% local; 10% foreign currency — confirmed in source Regs); Sections 44–45 refunds incl. Section 44(6) set-off and Section 44(7) freeze; SI 175/2007 30-day refund window.

Case law

• Delta Beverages 23-HH-577; Inamo 23-SC-096; Prosperous Days 21-HH-024 — currency matching. Redan 23-HH-637; SZ 20-HH-142 — Section 72 machinery. MR Bank 19-HH-779 — Section 71(2) proviso. Mayor Logistics 14-CC-007 — instalments. Packers International 16-SC-028 — nil returns. Section 37A line (CF, DNS, IAB, Nestlé) — return-is-assessment. None on the Single Account itself (stated honestly).

ZIMRA guidance

• Comprehensive Guide to the ZIMRA Self-Service Portal (local source): Single Account concept and allocation rule (§11.1), currency segregation (§11.2), Payments seven pages, Taxpayer Accounting four pages, monthly-reconciliation instruction, E-Messaging and Case Management routing, Debt Management pre-due-date advice.
• Official SSP online help unreachable this run — inter-head priority order, screen labels and filters flagged .