Choosing to deduct actual expenses looks like the smart decision on paper and fails constantly in practice. Not because the arithmetic is hard, but because when it's time to show proof, most freelancers have a bank statement and a memory.
This is about the part nobody teaches: the record system, not the tax theory.
The one principle underneath everything
A deductible expense must be incurred directly to earn that income, and you must be able to demonstrate three things at once:
- The payment happened. Money genuinely left your hands.
- Who was paid, and for what. You can identify the recipient and the nature of the spend.
- It relates to the work. You can explain how it produced income.
A bank transfer slip proves only the first. That's why a statement alone is never enough, and it's exactly where actual-expense claims collapse.
What counts as evidence
From strongest to weakest:
Full-form tax invoice (ใบกำกับภาษี). The best. It carries both parties' names, addresses and taxpayer IDs, with the goods or services clearly described. If you're VAT-registered it doubles as your input tax claim.
Receipt (ใบเสร็จรับเงิน). Fine. It should show the payee, the date, the amount, what was paid for, and ideally your name as payer.
Payment voucher (ใบสำคัญรับเงิน). For payees who can't issue receipts — a freelance photographer, a day-rate assistant. Have the recipient sign it, attach a copy of their ID, and state the work performed and the amount.
Certificate in lieu of receipt (ใบรับรองแทนใบเสร็จรับเงิน). For spending that genuinely has no receipt — taxis, coin parking. Legitimate, but it should be a small share. If half your expenses look like this, that's a warning sign.
A bare transfer slip. The weakest. Supporting evidence, never standalone proof.
Five things that break the system
1. Running work through your personal account
If client payments, rent, lunch and subcontractor fees all move through one account, separating them costs you hours every time — and you'll never separate them completely.
A dedicated business bank account is a one-hour investment that pays out annually. If you're VAT-registered, add a second place to park collected VAT, because that money isn't yours.
2. Not recording which job the money went to
A THB 4,500 font purchase means nothing on its own. "Font licence for Client A's rebrand" means something immediately. Tag every expense you can with a client or project.
Beyond tax, this tells you which jobs are actually profitable and which ones only look profitable.
3. Ignoring mixed-use assets
Laptop, phone, car, home internet — all used for both work and life. Claiming 100% with no reasoning behind it is the most commonly challenged position there is.
The safer approach is a defensible percentage applied consistently: one phone line used 70% for work, with the reasoning written down. Consistency matters more than decimal precision. The worst pattern is 100% this year and 40% next year with no explanation for either.
For assets with a multi-year life — an expensive machine, for instance — talk to a bookkeeper about writing it off over its useful life rather than all at once.
4. Storing documents somewhere unsearchable
A downloads folder with 400 files named receipt(3).pdf is not a filing system.
What you need is one location, one naming convention, and a link to a client or project. A convention that works well: date, payee, amount — 2026-08-01_adobe_1690.pdf.
Photographing paper receipts the moment you receive them is the highest-return habit here. Thermal paper from card terminals fades to illegible within months, and an unreadable receipt is the same as no receipt.
5. Not keeping things long enough
Assessment officers can generally look back within the periods set by law, extending to five years in certain cases, and VAT-registered operators are required to retain records for at least five years.
The simplest workable policy: keep everything for five years, full stop. Don't spend energy deciding which document needs which retention period. Storage is cheaper than the decision.
The 30-minute monthly routine
A system that takes ninety minutes a month is one you'll abandon by month three. This one survives.
Minutes 1–10, collect. Open your statement, walk the business expenses, and match each to evidence. Anything missing, request it now. The sooner you ask, the easier it is to get.
Minutes 11–20, label. Give every line an expense category and a client or project.
Minutes 21–25, reconcile. Recorded expenses should be close to what actually left the business account. A big gap means something is missing.
Minutes 26–30, read two numbers. Cumulative revenue for the year so far and how far it is from THB 1.8 million; and actual expenses as a percentage of revenue.
That second number quietly answers the most expensive question of your year, months in advance.
The number that decides actual versus lump-sum
If your documented actual expenses come in below the lump-sum rate available to you, claiming actuals is extra work in exchange for a bigger tax bill. There's no reason to do it.
So track that percentage monthly instead of discovering it in March. If by August you can see actual expenses running at 25% of revenue, you can stop chasing every small receipt for the year with a clear conscience.
And if it's at 55%, you know every lost receipt has a real price attached.
Red flags worth fixing first
- Large expenses supported by nothing but a transfer slip
- Subcontractors paid in cash with no signed voucher and no withholding tax remitted
- Expenses paid from someone else's account — a spouse's, say — but claimed under your name
- Any expense whose connection to your work you can't explain in one sentence
- Receipts issued in someone else's name
Every one of these is far easier to fix in the month it happens.
Start with three things today
- Open a separate business bank account and move every client onto it.
- Set up one document location with a naming convention, and photograph paper receipts on receipt.
- Block 30 minutes at month end in your calendar — and actually do it three months running.
Those three moves take you from someone reconstructing a year in March to someone who always knows their own numbers.
In MANA, expenses attach to clients and projects natively; you can photograph several receipts at once and have the data extracted for your review rather than trusted blindly, with the original file kept alongside the record in your own storage. Which means the hardest question in this whole topic — where is the evidence for this line — always has the same answer.