How to Build Accounting in Google Sheets and Excel

The Two Paths: Manual vs. Agent-Driven Accounting

If you’re a founder, agency owner, or marketer, your accounting spreadsheets usually start as a survival tool: a single Google Sheet or Excel file that somehow holds the truth about your cash, clients, and runway. Over time, that single file becomes an ecosystem—tabs for invoices, payroll, ad spend, retainers, renewals.

You can manage this world in two ways:

1. Manually (you or your team do every step).
2. At scale with an AI computer agent like Simular that operates your spreadsheets for you.

Below, we’ll walk through both, so you can decide what to keep human and what to delegate.

Manual Way #1: Build a Clean Accounting Base Sheet

Goal: Create a single source of truth for income and expenses.

Steps (Google Sheets or Excel):

1. Create a new workbook. Name it something clear like “2025 Master Accounting”.
2. Add core tabs: Transactions, Chart_of_Accounts, Summary.
3. Design the Transactions tab: Add headers: Date, Description, Category, Subcategory, Payment Method, Amount In, Amount Out, Client/Project, Notes.
4. Lock your structure: Freeze the header row and turn the range into a Table (Excel) or use Filters (Sheets) for easier sorting.
5. Add data validation: Use dropdowns for Category and Client to avoid typos.
6. Create summary formulas: In the Summary tab, use SUMIF/SUMIFS to total revenue, expenses, and profit by month.

Pros: Full control, transparent logic, easy to customize.
Cons: Time-consuming to keep updated, error-prone when you’re rushed.

Manual Way #2: Use Templates for Specific Accounting Tasks

Instead of reinventing the wheel, use dedicated sheets for:

• Profit & Loss: Track revenue, COGS, and operating expenses month by month.
• Cash Flow: Follow money in and out across operations, investing, and financing.
• Accounts Receivable: List who owes you, due dates, and days outstanding.
• Accounts Payable: Track bills, vendors, terms, and upcoming payments.

Steps:

1. Start from a reputable template (Microsoft, Smartsheet, Financial Cents, etc.).
2. Customize categories to match your chart of accounts.
3. Link these templates back to your master Transactions tab using formulas or references.

Pros: Faster setup, battle-tested structures, easier to train team members on.
Cons: Still manual data entry; templates can drift out of sync if not maintained.

Manual Way #3: Reconciliation Rituals (Monthly or Weekly)

No spreadsheet is useful if it doesn’t match reality.

Steps:

1. Download bank and card statements as CSV.
2. Import into a temporary tab (e.g., Bank_Import_May).
3. Use formulas (VLOOKUP/XLOOKUP, INDEX/MATCH) to match imported lines with your Transactions table.
4. Highlight unmatched entries and either add them or investigate.
5. Confirm that ending balances match your statements.

Pros: Strong control and understanding of your numbers.
Cons: Tedious; easy to procrastinate; late reconciliations mean late insights.

Where Manual Work Breaks Down

Manual workflows are fine when:

• You have a single business or a small client roster.
• Transaction volume is low.
• You’re okay trading your evenings for accuracy.

They start to hurt when:

• You manage multiple entities or clients.
• You’re pulling data from many sources (banks, Stripe, PayPal, ad platforms).
• Reporting frequency increases (weekly dashboards, investor updates, client reports).

This is when you need more than formulas—you need a helper that actually uses the computer for you.

Automated Way #1: Let an AI Agent Populate Your Spreadsheets

Simular’s AI computer agents can operate across your desktop, browser, Google Sheets, and Excel the way a trained finance assistant would.

Example Workflow:

• Every Monday, the agent:
  • Logs into your bank and downloads CSVs.
  • Opens your master Excel workbook.
  • Pastes new transactions into the Transactions tab.
  • Categorizes lines based on your rules and past behavior.
  • Updates your P&L and cash-flow tabs.

Pros:

• Saves hours of repetitive work.
• Reduces copy/paste mistakes.
• Works across tools without needing rigid APIs.

Cons:

• Requires an initial setup and testing phase.
• You still need to design good spreadsheet structures.

Automated Way #2: Agents for Multi-Client or Multi-Brand Accounting

For agencies and firms, the real magic is scale.

Pattern:

1. Standardize a “client accounting pack” in Google Sheets or Excel: same tabs, same headers, same formulas.
2. Show the Simular agent how you:
   • Pull data from bank portals, payment processors, or ad platforms.
   • Copy or transform that data into client-specific workbooks.
   • Generate monthly summary views.
3. Let the agent repeat this workflow across all clients.

Now the cost of adding another client or brand is measured in agent minutes, not your weekend hours.

Automated Way #3: Continuous QA With Transparent Execution

Simular Pro is designed for production-grade reliability and transparent execution. That means you can:

• Inspect every step: See each click, keystroke, and formula the agent touches.
• Set guardrails: Require human review before sending critical reports or large payments.
• Refine over time: Adjust instructions when you change your chart of accounts or pricing model.

Pros:

• Audit trail for every automated run.
• Easier compliance and handoff to external accountants.

Cons:

• You’ll want a short learning curve to understand the agent’s logs and controls.

When to Let Go (Without Losing Control)

A useful rule of thumb: if a step in your accounting spreadsheet

• happens more than twice a month,
• follows the same clicks and keystrokes,
• and stresses you out when you’re tired,

then it’s a prime candidate for delegation to an AI agent.
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Your job becomes designing the system: choosing templates, defining categories, and deciding what “good” looks like. The agent’s job is to push the buttons, reconcile the rows, and keep everything updated across Google Sheets and Excel.
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That’s how you move from surviving in spreadsheets to running a business that actually uses them as a strategic advantage.