Quick Start Guide
Before You Begin
This file uses protected dynamic array formulas. Only enter data in the light yellow cells. Never delete or overwrite any column marked with a lock icon. Always follow the Zero-Data Reset before entering live data.
Make Your Copy
Open the link in your delivery email and click File → Make a Copy to save it to your Google Drive. (If you prefer Microsoft Excel, download as .xlsx).
Run the Zero-Data Reset
Navigate to the 02_CASH_FLOW_LOG tab. Highlight only the light yellow cells in Columns A to G (Row 2 downward) and press Delete. Do not touch Column H. Repeat this for the yellow cells in Columns A to E on the 04_PROJECT_MARGINS tab. Do not delete header rows.
Set Your Starting Position
Go to the 01_DASHBOARD tab. Enter your liquid cash balance in Cell B3. Set your forecast base date (today) in H2. Select UK_SATR as your Tax Regime for UK Self Assessment, and leave Scenario as Expected.
Log Your First Transactions
Go to 02_CASH_FLOW_LOG. Enter each income or expense in a new row (YYYY-MM-DD), select a category from Column D, and assign a project code in Column F. Your 52-week cash curve on the dashboard will update automatically.
Check Your Tax Provision
Go to 03_TAX_MODEL. Your quarterly tax liability is calculated automatically. Set aside the Required Provision figure for each quarter into a separate savings account. Do not spend this cash.
CRITICAL RULES
- Never delete Column H in the Cash Flow Log.
- Never delete Column F or G in the Project Margins tab.
- Always confirm the Unallocated Cash Audit cell reads £0.00 before trusting dashboard figures.
- If the dashboard shows all zeros after data entry, check that your dates are in YYYY-MM-DD format.
UK Self Assessment (2026/27)
The engine calculates your gross revenue, taxable operating expenses, taxable net income, and the exact provision you need to set aside each quarter to meet your Self Assessment liability without a shortfall.
Tax Bands (England, Wales, NI)
| Personal Allowance (up to £12,570) | 0% |
| £12,571 to £50,270 | 20% |
| £50,271 to £125,140 | 40% |
| Over £125,140 | 45% |
Key Dates
- 5 Oct: Tell HMRC you need to complete a return.
- 31 Oct: Paper tax return deadline.
- 30 Dec: Online filing deadline (if collecting via PAYE).
- 31 Jan: Online return deadline; balancing payment & first payment on account.
- 31 Jul: Second payment on account.
Payments on Account
HMRC collects Income Tax and National Insurance twice per year. Each payment is usually 50% of your prior year's qualifying tax bill. The engine provisions for all four quarters so cash is ring-fenced in advance.
Build your tax reserve from every payment received.
Protect cash after the 31 July payment on account.
Prepare return information and check YTD provision.
Fund the 31 January balancing payment.
Deductible Expenses
- Software subscriptions directly used in work
- Equipment purchased solely for business
- Home office costs (proportional)
- Travel costs incurred for client work
- Professional development & training
- Marketing, advertising, and accountancy fees
Note: The engine does not currently calculate VAT on individual transactions. Log net-of-VAT figures if registered.
Routine Checklist
- Select UK_SATR in the Dashboard.
- Update income and allowable costs consistently.
- Check Required Provision in 03_TAX_MODEL.
- Transfer tax reserves to a separate account.
- Treat tax-provision cash as unavailable.
- Review position before major withdrawals.